Small-cap biotech stocks are in a rut, confirming the frustration expressed by a number of biotech investors and traders these days. 

Before I dig into specific numbers, let's pull back for some perspective. Biotech stocks overall are still trouncing the broader market this year, so complaints about small-cap biotech stocks is a bit of a first-world problem. 

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Admittedly, the picture doesn't look as pretty for the past three months. 

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The orange line represents the iShares Nasdaq Biotechnology ETF(IBB) - Get Report , which is more heavily weighted toward large-cap biotech stocks. In contrast, the SPDR S&P Biotech ETF(XBI) - Get Report (blue line) includes many more small-cap biotech stocks. In the last three months, the XBI is down almost 3%, underperforming the IBB and the S&P 500

To dig into the diverging performances of small- and large-cap biotech stocks, I ran two screens using S&P Capital IQ. The first screen identified biotech stocks trading on major U.S. exchanges with market capitalizations of $500 million or greater. This was my proxy for large-cap biotech stocks, although admittedly, my market cap cutoff is somewhat arbitrary. The screen identified 165 stocks. The average return for these large-cap biotech stocks in the past three months was 5%. 

The second screen picked up 279 "small cap" biotech stocks trading on major U.S. exchanges with market caps below $500 million. The average three-month performance for these stocks: -19%.

There's your divergence. If you feel like it's harder to make money in small-cap biotech today, you're right, it is. 

In case you're wondering, the best-performing, small-cap biotech stocks for the past three months are Ambit Biosciences (AMBI) , iBio(IBIO) - Get Report , Esperion Therapeutics(ESPR) - Get Report , OvaSciences (OVAS) and MediciNova(MNOV) - Get Report . Worst performers in the sub-group: WaferGen Biosystems (WGBS) , Sunesis Pharma(SNSS) - Get Report , Cytori Therapeutics (CYTX) , Cellectar Biosciences(CLRB) - Get Report and Alcobra (ADHD) .

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback;

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