Nasdaq Biotechnology Index: Holdings, Weighting and Risks

The well-known iShares biotech ETF IBB stopped tracking the Nasdaq Biotechnology Index in June 2021, yet it is still often named as an NBI fund. That alone shows how easily a biotech index and a fund get mixed up. The NBI itself is a stock index with clear rules: it bundles biotechnology and pharmaceutical companies listed on Nasdaq and behaves quite differently from a single biotech stock.

This guide explains what is inside the NBI, how Nasdaq weights it and which funds really track it. You will see the selection rules, the weighting caps, the largest declines since 2003 and a comparison with the Nasdaq-100, based on the official index history. This article follows our editorial policy and is for education, not investment advice.

Nasdaq Biotechnology Index in 30 seconds

• A sector benchmark. The NBI tracks biotechnology and pharmaceutical companies listed on Nasdaq. Nasdaq has calculated it since 1 November 1993.
• No fixed number of members. Every security that meets the rules is included. On 28 October 2026 there were 245 members; the yearly review is in December.
• Market-cap weighted with caps of 8 and 4 percent. Only the five largest may weigh more than 4 percent. On 30 September 2026, Gilead, Amgen and Vertex led with 8.16, 7.85 and 7.69 percent; the top five made up 33.8 percent.
• Deep, slow declines. Since 2003 the NBI fell more than 25 percent four times; after the 39.4 percent drop from July 2015 to June 2016, a new high came only in May 2020.
• Check the ETF’s index. IBB now tracks an NYSE index; Invesco’s IBBQ and the UCITS ETFs BTEC and SBIO track versions of the NBI.

What is the Nasdaq Biotechnology Index?

The Nasdaq Biotechnology Index is a stock index that tracks the price of biotechnology and pharmaceutical companies listed on Nasdaq. Nasdaq calculates it under the symbol NBI and weights its members by market value with caps.

The NBI is not a security you can buy; it is a yardstick for the sector. To trade it you need a product that tracks it, such as an ETF. According to Nasdaq’s index overview, the index started on 1 November 1993 at 200 points. It closed at 7,256 points on 28 October 2026 and is recalculated once per second on US trading days.

Despite its name, the NBI also holds pharmaceutical companies. Eligible are securities classified under the Industry Classification Benchmark (ICB) as either biotechnology or pharmaceuticals. So the index covers young research firms as well as established drug makers with large sales.

What counts is the listing, not the headquarters. A company’s US listing must be exclusively on Nasdaq, in the Global Select Market or the Global Market. That is why foreign companies such as BioNTech from Mainz, argenx or Sanofi are included through their US depositary receipts. Large drug makers listed on the New York Stock Exchange, such as Eli Lilly or Pfizer, are not.

Which stocks are in the Nasdaq Biotech Index?

The NBI includes every security that meets the rules; there is no maximum number. Nasdaq’s index methodology sets the eligibility rules. Once a year Nasdaq checks all candidates, and those that pass are included.

• Industry: ICB biotechnology or pharmaceuticals subsector.
• Listing: US listing only on Nasdaq Global Select Market or Global Market. Common stocks, ADRs and some other share types are eligible; if an issuer has several share classes, all of them.
• Size: at least $200 million market value.
• Trading: an average of at least 100,000 shares a day, measured from the start of the year to the reference date.
• Trading history: at least three full calendar months, not counting the month of listing.

An ADR (American depositary receipt) is a certificate traded on a US exchange that represents shares of a foreign company. For ADRs, Nasdaq counts only the depositary shares actually issued, not all shares of the group. A large foreign company can therefore weigh much less in the NBI than its total market value suggests.

The number of members changes from year to year. On 28 October 2026 Nasdaq’s member list showed 245 securities. The annual reconstitution is announced in early December and takes effect after the close on the third Friday of December. If a company is taken over during the year, Nasdaq removes it as soon as the deal is considered highly probable, and it is replaced only at the next reconstitution.

Company	Symbol	Weight
Gilead Sciences	GILD	8.16%
Amgen	AMGN	7.85%
Vertex Pharmaceuticals	VRTX	7.69%
Moderna	MRNA	5.04%
Regeneron Pharmaceuticals	REGN	5.03%
Revolution Medicines	RVMD	2.88%
Illumina	ILMN	2.71%
Biogen	BIIB	2.19%
Alnylam Pharmaceuticals	ALNY	2.16%
Roivant Sciences	ROIV	1.73%

The ten largest NBI members according to Nasdaq’s factsheet as of 30 September 2026, together 45.44 percent of the index. Weights change with every price; Nasdaq publishes the current member list.

The top five make up almost 34 percent, the top ten just over 45 percent. The other 235 or so members share the rest. Reading the NBI therefore means reading mostly Gilead, Amgen and Vertex, plus a long tail of smaller biotech firms, many of which have no drug on the market yet. Older factsheets with other leaders describe a past state and are not today’s list.

How is the NBI calculated and weighted?

A modified market-cap weighted index first weights each stock by its market value and then caps single weights at fixed limits, so size still matters but no single member dominates.

The NBI applies its caps in two stages. First, each member gets the weight that matches its market value relative to all members. In the first stage, any weight above 8 percent is capped. In the second stage, the five largest keep their weight and all others are limited to 4 percent.

Rule	Value
Maximum weight per member	8%
Members above 4%	at most the five largest
All others	at most 4%
Rebalancing	quarterly, effective after the third Friday of March, June, September and December
Reconstitution	once a year, effective after the third Friday of December, market data as of end of October

Weighting and review rules according to Nasdaq’s index methodology, read on 29 October 2026; the latest change entry shown in the document is dated 19 March 2024.

Between reviews, weights can drift above their caps. Nasdaq calculates each rebalancing with shares and prices from the prior month end, so end of February, May, August and November. After that, weights move with prices. That is why Gilead stood at 8.16 percent on 30 September, slightly above the 8 percent cap; the next rebalancing in December spreads the excess again.

A price index tracks only price changes, while a total return index also reinvests dividends. The familiar NBI level is a price index. According to Nasdaq’s index versions, there is also the total return index XNBI, which reinvests dividends on the ex-date, and a net version, XNBINNR, which reinvests 70 percent of dividends after an assumed 30 percent tax. Many biotech firms pay no dividend, so the versions are not far apart, but when you compare returns you should know which one you are looking at.

How has the Nasdaq Biotechnology Index performed?

Over the long run the NBI has risen strongly, but with long dry spells. Nasdaq’s freely available daily series starts on 21 January 2003 at 515 points. The record close came on 19 August 2026 at 7,405 points; on 28 October the index was about 2 percent below it. The chart uses a log scale, on which equal percentage moves look equally large, and marks the four largest declines in orange.

The series shows four declines of more than 25 percent since 2003. Each is measured from the highest close up to then to the lowest close before the next high. What stands out is less the depth than the duration: after the July 2015 high it took almost five years to reach a new record, after the August 2021 high just over four years.

High to low	Decline	New high
07/2015 to 06/2016	−39.4%	05/2020
08/2021 to 06/2022	−38.5%	11/2025
08/2008 to 03/2009	−34.7%	03/2010
04/2004 to 08/2004	−26.9%	02/2006

The four NBI declines of more than 25 percent since 21 January 2003 (high and low: 20 Jul 2015 and 27 Jun 2016, 9 Aug 2021 and 13 Jun 2022, 14 Aug 2008 and 9 Mar 2009, 27 Apr 2004 and 9 Aug 2004), daily closes from Nasdaq’s index history, price index in US dollars. New high: first close above the old record. Own calculation as of 28 October 2026.

Year	NBI	Nasdaq-100
2008	−12.6%	−41.6%
2013	+66.0%	+36.9%
2016	−21.3%	+7.3%
2022	−10.1%	−32.4%
2023	+4.6%	+55.1%
2025	+33.4%	+21.0%
2026 to 28 Oct	+27.7%	+18.7%

Calendar-year change, close to close, total return indices XNBI and XNDX with dividends reinvested, in US dollars. Calculated from Nasdaq’s daily series as of 28 October 2026; own calculation.

As a whole, the NBI swings less wildly than its reputation suggests. Nasdaq’s factsheet gives an annualized volatility of 23.37 percent for the ten years to September 2026 and an average return of 9.64 percent a year, both for the total return index XNBI. By our calculation, volatility from 25 September 2003 to 28 October 2026 was 23.7 percent for the NBI and 21.9 percent for the Nasdaq-100 (standard deviation of daily log returns, annualized, both as total return indices). These figures describe the past, not the future; with drawdowns this long, your position size matters.

The calm of the index does not apply to its single stocks. A small biotech firm with one drug candidate can lose a large part of its value in a day after a failed clinical trial. In the NBI such a member barely registers, because it weighs only a fraction of a percent. The event risk of the single stock does not disappear in the index; it is diluted.

NBI vs Nasdaq-100

The Nasdaq-100 holds some biotech stocks, but technology dominates it; the NBI is pure biotech and pharma. Setting both indices to the same start value shows when biotech led or lagged the wider market. The chart compares both as total return indices with dividends, both starting at 100 on 25 September 2003.

Since September 2003 the NBI grew 10.8-fold and the Nasdaq-100 27.4-fold. Biotech led during parts of the period around 2015; after that, the technology market pulled far away. Since the end of 2015 the NBI gained 120 percent and the Nasdaq-100 just over 600 percent. The NBI did better in ten of the 23 years from 2004 to 2026, counting 2026 only to 28 October.

In return, the NBI fell less in the big crises. In 2008 it lost 12.6 percent while the Nasdaq-100 lost 41.6 percent; in 2022 it was 10.1 against 32.4 percent. The largest decline of the total return index since 2003 was 39.2 percent, against 53.4 percent for the Nasdaq-100. Medicines are needed in a recession too, which supports the large pharma names. That is no guarantee for the next crisis.

Divide the NBI by the Nasdaq-100 and you get biotech’s relative strength. The line shows whether the biotech and pharma stocks in the NBI are doing better or worse than the Nasdaq-100, as explained in our guide to relative strength. It does not measure money flowing in or out, and it is not an early warning: it shows which group is doing better now, not when a trend ends.

A different biotech index can paint a very different picture. The S&P Biotechnology Select Industry Index, which the XBI ETF tracks, holds only biotech without pharma and weights its members roughly equally. There, a small research firm counts almost as much as a large company; in the NBI the heavyweights dominate. Neither is the better index; they measure different things. Our Nasdaq-100 forecast covers the tech index itself.

What moves biotech stocks and the NBI?

Biotech prices depend on events that no chart predicts. Five forces shape the sector. They show up first in trial data, regulatory decisions and quarterly results, and only then in the price.

• Clinical trials: a drug candidate goes through several test phases in humans. Good or bad data move small members with few projects most.
• Approval: in the US, the FDA reviews the data and decides on approval. The date is often known, the outcome is not.
• Patents: when protection for a best-selling drug ends, cheaper copies can follow. This hits mainly the large members with high index weights.
• Financing: many small firms are not yet profitable and need fresh capital. Whether they get it, and at what price, also depends on the mood in capital markets.
• Takeovers: large companies buy research firms to fill their pipelines. For the target that often means a price jump, for the index a departure.

Takeovers change the NBI directly. According to the methodology, Nasdaq removes a company as soon as a takeover is considered highly probable, for example after regulatory approval. A replacement comes only at the next reconstitution in December, so the number of members can shrink during the year.

Key dates are the earnings of the heavyweights and the review dates. Because Gilead, Amgen, Vertex, Moderna and Regeneron make up about a third of the index, their quarterly reports move the whole NBI. So do the rebalancings in March, June, September and December, when index funds adjust their holdings.

How to invest in the Nasdaq Biotechnology Index

You cannot buy the NBI directly, only products that track it. Many biotech ETFs have similar names and still follow different indices. The list shows which index the best-known funds track according to their providers, read on 29 October 2026.

• iShares IBB (US): NYSE Biotechnology Index, not the NBI.
• SPDR XBI (US): S&P Biotechnology Select Industry Index, not the NBI.
• Invesco IBBQ (US): Nasdaq Biotechnology Index, so it tracks the NBI.
• iShares BTEC (UCITS, Europe): net version of the Nasdaq Biotechnology Index.
• Invesco SBIO (UCITS, Europe): Nasdaq Biotechnology total return index.

Index according to each provider’s product page or factsheet and Nasdaq’s product list, read on 29 October 2026. ISINs of the UCITS ETFs: iShares Nasdaq US Biotechnology UCITS ETF IE00BYXG2H39, Invesco Nasdaq Biotech UCITS ETF IE00BQ70R696.

The best-known biotech fund no longer tracks the NBI. According to the iShares product page, the iShares Biotechnology ETF with the symbol IBB has tracked the NYSE Biotechnology Index since 21 June 2021; before that, its benchmark was the NBI. An NYSE article describes how the switch reshaped the biotech index landscape. Nasdaq’s product list no longer shows IBB as an NBI fund, but it does list the Invesco Nasdaq Biotechnology ETF, IBBQ.

Outside the US, access depends on local rules. In the European Union, retail brokers generally cannot offer a fund to retail investors without the key information document that the PRIIPs regulation requires, and US-domiciled ETFs usually do not provide one. Unlike for the SOX, two European UCITS ETFs track the NBI. Whether your broker offers them is best checked with the ISIN.

The two UCITS ETFs track different versions of the NBI. According to its factsheet, the iShares Nasdaq US Biotechnology UCITS ETF buys the stocks itself and measures itself against the net version of the index. The Invesco Nasdaq Biotech UCITS ETF tracks the total return index XNBI synthetically, through swaps with banks. The index itself is in US dollars, so investors in other currencies also take on currency risk.

When you choose a fund, check its index in the factsheet, not just its name. A fund on a roughly equal-weighted biotech index behaves differently from one on the NBI with its heavyweights. Check the costs and the replication method in the provider’s documents. Our SOX index guide explains the same trap for semiconductor ETFs.

Strengths and limits of the NBI

The NBI is a good benchmark for biotech on Nasdaq, but not a picture of the whole healthcare sector. It bundles about 245 biotech and pharma stocks in one number, its rules are public with clear caps and fixed review dates, and it dilutes the trial and approval risk of single firms. Compared with the Nasdaq-100, it shows whether biotech leads or lags.

Its limits are just as clear. It includes only Nasdaq-listed stocks, so large drug makers on the NYSE are missing. The top five make up about a third, while the many small firms weigh little. After its large declines since 2003, it took up to five years to reach a new high, and a comparison with other indices describes the past, not a reliable signal for tomorrow.

Nasdaq Biotechnology Index: my conclusion

The NBI is the sector gauge for biotech and pharma on Nasdaq. It includes every security that meets its rules, weights them by market value with caps of 8 and 4 percent, and is shaped strongly by a few heavyweights such as Gilead, Amgen and Vertex.

As a whole it is calmer than its single stocks, but not without risk. Since 2003 it fell more than 25 percent four times, and twice the recovery took more than four years. When you invest, the index is in the small print: the well-known IBB no longer follows the NBI, so check the factsheet, the return version and whether the product is available to you.

Frequently asked questions about the Nasdaq Biotechnology Index

What does the Nasdaq Biotechnology Index measure?

It tracks the price of biotechnology and pharmaceutical companies listed on Nasdaq. The NBI is a stock index that Nasdaq has calculated since 1 November 1993. It weights its members by market value with caps.

How many stocks are in the NBI?

There is no fixed number. The NBI includes every security that meets its rules; on 28 October 2026 there were 245 members. Nasdaq reselects them once a year in December, and companies that are taken over leave earlier.

Which are the largest stocks in the Nasdaq Biotech Index?

The three largest were Gilead, Amgen and Vertex. On 30 September 2026, Gilead Sciences weighed 8.16 percent, Amgen 7.85 and Vertex 7.69 percent, followed by Moderna and Regeneron. Nasdaq publishes the current list.

Does the iShares IBB ETF track the Nasdaq Biotechnology Index?

IBB no longer tracks the NBI. According to iShares, IBB has tracked the NYSE Biotechnology Index since 21 June 2021; before that it tracked the NBI. A US ETF that tracks the NBI is Invesco’s IBBQ.

Is the NBI the same as XBI?

XBI is an ETF tracking a different biotech index. It follows the S&P Biotechnology Select Industry Index, which holds only biotech without pharma and weights its members roughly equally. In the NBI, the large members dominate.

Is the NBI more volatile than the Nasdaq-100?

As a whole, only slightly. From 25 September 2003 to 28 October 2026, the annualized volatility of the total return index was 23.7 percent for the NBI and 21.9 percent for the Nasdaq-100, by our calculation, and the NBI’s largest decline was smaller. Single biotech stocks are a different matter: their event risk around trial data and approvals is far higher.