These are the best and worst-performing medical and biotech stocks in February 2013. We ran a screen of biotechnology and medical companies traded on the New York Stock Exchange, the Nasdaq or the American Stock Exchange that had market capitalizations of more than $300 million at the beginning or end of the month. The data come from Interactive Data and Thomson Reuters Fundamentals via FactSet Research Systems. February's Best-Performing Biotech Stocks Company Ticker 1-month price change% 52-week price change % Recent Market Value ($MIL) Optimer Pharmaceuticals Inc. OPTR 30.6 -28.5 578.0 Questcor Pharmaceuticals Inc. QCOR 27.9 -28.1 1,905.5 Celldex Therapeutics Inc. CLDX 27.6 57.4 590.0 Pharmacyclics Inc. PCYC 26.6 277.2 6,117.9 Taro Pharmaceutical Industries Ltd. TARO 22.3 46.9 2,537.1 February's Worst-Performing Biotech Stocks Company Ticker 1-month price change% 52-week price change % Recent Market Value ($MIL) OraSure Technologies Inc. OSUR -21.1 -36.6 306.8 Synta Pharmaceuticals Corp. SNTA -23.3 143.0 531.7 Keryx Biopharmaceuticals Inc. KERX -29.2 167.8 462.5 Dynavax Technologies Corp. DVAX -34.0 -11.2 364.6 Affymax Inc. AFFY -85.9 135.4 98.5