Year-to-date gain: 16.8 percent
AUM: US$7.82 billion

Launched in 2006, the SPDR Biotech ETF tracks the performance of the S&P Biotechnology Select Industry Index, focusing exclusively on US stocks. The fund has an expense ratio of 0.35 percent, and its five year return comes in at 5.01 percent.

Of the fund's 144 holdings, 76 percent are large and mid-cap companies. The fund's top holdings include Incyte (NASDAQ:INCY), United Therapeutics (NASDAQ:UTHR) and Gilead Sciences (NASDAQ:GILD).

Year-to-date gain: 13.1 percent
AUM: US$1.21 billion

The First Trust NYSE Arca Biotechnology Index Fund tracks the price and yield of an equity index called the Amex Biotechnology Index. Founded in 2006, the fund’s expense ratio is 0.56 percent. Its five year return comes in at 6.71 percent.

With 31 holdings, this fund is much smaller than the other ETFs on this list. It is primarily focused on large-cap US biotech companies, although it has exposure to some firms in Europe. Its top holdings include Exelixis (NASDAQ:EXEL), Intra-Cellular Therapies (NASDAQ:ITCI) and Incyte.

Year-to-date gain: 11.9 percent
AUM: US$17.95 billion

The Vanguard Health Care Index Fund ETF is a broad fund with healthcare firms from varied industries that came to market in 2004. It's achieved returns of 11.07 percent over the last five years. The ETF’s expense ratio is very low at 0.1 percent.

At 414, this fund has the most holdings of the life science ETFs on this list, with more than 86 percent being large-cap companies predominantly in the United States. Its top holdings by weight include Eli Lilly (NYSE:LLY), UnitedHealth Group (NYSE:UNH) and AbbVie (NYSE:ABBV).

Year-to-date gain: 11.7 percent
AUM: US$4.9 billion

The iShares US Medical Devices ETF was launched in 2006 and, as the name suggests, focuses on medical device companies in the United States. The fund's five-year return stands at 8.27 percent. This biotech ETF has an expense ratio of 0.4 percent.

This biotech fund is concentrated on large-cap companies, representing 89 percent of its holdings. Its top holdings by weight include Abbott Laboratories (NYSE:ABT), Intuitive Surgical (NASDAQ:ISRG) and Stryker Corporation (NYSE:SYK).

Year-to-date gain: 11.7 percent
AUM: US$3.36 billion

The iShares US Healthcare ETF launched in 2000, making it the longest-running ETF on this list. EFTdb.com warns investors that "IYH probably doesn’t have much use for those constructing a long-term, buy-and-hold portfolio; this ETF is a more useful tool for those looking to establish a tactical tilt towards health care or for use in a sector rotation strategy."

The fund has an expense ratio of 0.39 percent, and a five-year return rate of 11.12 percent. Of its 109 holdings, 94 percent are large-cap companies. Its top holdings by weight are Eli Lilly, UnitedHealth Group and Johnson & Johnson (NYSE:JNJ).