XBI vs IBB: Which Biotech ETF Is Which?
XBI and IBB are the two best-known biotech ETFs. XBI gives its stocks roughly equal weight, so small and mid-size biotechs drive it. IBB weights by company size, so a handful of large biotechs drive it. That makes XBI the more volatile of the two: it falls harder in bad years and rises harder in good ones.
How XBI and IBB are built
XBI holds well over a hundred biotech stocks and gives each one roughly the same weight. A $2 billion clinical-stage company counts about as much as a $200 billion one. That makes XBI a bet on the smaller, trial-driven part of the sector.
IBB weights by market value, with caps on the biggest names. Large, profitable biotechs make up a big share of it, so it moves more like an established industry and less like a basket of trial results.
XBI vs IBB in numbers
Price changes from our own market data:
| Period | XBI / IBB |
| First half of 2022 (Jan 3 to Jun 16) | -44.6% / -30.6% |
| June 2022 to March 2026 | +72.0% / +43.5% |
| 2024 (calendar year) | +0.9% / -2.7% |
| 2025 (calendar year) | +35.4% / +27.7% |
| Yearly volatility, 2022 to 2026 | 32% / 22% |
XBI fell much harder in the 2022 sell-off, then recovered much more. Its daily swings were about half again as large as IBB's.
Which one fits what you want
- XBI tracks small and mid-size biotechs, so it reflects trial results and takeovers most, with deep drops along the way.
- IBB tracks the sector with less of a ride, led by companies that already sell drugs.
- Either one works as a benchmark. When you judge a single biotech stock, compare it with XBI: a stock that rose 20% while XBI rose 30% underperformed.
In our checklist test, even stocks with 10 or more boxes green beat XBI less than half the time over six months. Beating the sector with single stocks is hard.
See it live: Today's biggest biotech moves, to see what is pushing the sector and the ETFs.
Open Market Movers →Frequently asked questions
XBI weights its stocks roughly equally, so small and mid-size biotechs drive its returns. IBB weights by company size, so large biotechs dominate. XBI is the more volatile of the two.
Neither is better in every year. From June 2022 to March 2026, XBI rose 72% and IBB 43.5%, but in the first half of 2022 XBI fell 44.6% against 30.6% for IBB. It depends on how much swing you can live with.
It spreads money across well over a hundred biotechs, so one failed trial barely shows. It is still a volatile fund that has fallen more than 40% in a few months.
Because it gives small, trial-driven companies as much weight as large ones, and small biotechs move much more on news.
Compare a stock's return with XBI's over the same period. If biotech as a whole rose more than your stock, the stock lagged, even if it went up.
Educational content only. Not financial advice. Past results don't predict future ones.