The purpose of this study was to analyze sperm quality parameters and intersex severity of smallmouth bass in the South Branch of the Potomac River, and to determine if contaminants present in this river negatively affect these parameters. Samples were collected by boat electrofishing in May 2006 from three sites in the South Branch of the Potomac River and one site in the Gauley River. The three South Branch sites are in areas with historically high intersex occurrence. The site on the Gauley serves as the reference site. Gonads were collected from 38 male fish. Samples were split, one gonad sent to USGS National Wetlands Research Center, Lafayette, Louisiana, for testing of sperm quality parameters, such as motility, viability, count and maturity, and one gonad maintained at USGS Leetown Science Center for histological analysis. Sperm morphology was analyzed and rank of severity of intersex was assigned for each sample. Data from a separate study involving passive samplers deployed by the United States Geological Survey and West Virginia Department of Environmental Protection provided contaminant information for the sampling sites. Kruskal-Wallis analysis indicates that there are significant differences among sites with regard to motility (p=0.011), progressive motility (p=0.001), viability (p=0.039), and intersex (p<0.001). The severity of intersex within the experimental sites follows the pattern of contamination, with Petersburg, West Virginia being highest, Springfield, WV being lowest, and Moorefield, WV intermediate. Regression analysis shows there are significant relationships between motility and intersex (R²=0.322, p<0.001), progressive motility and intersex (R²=0.117, p=0.041), and viability and intersex (R²=0.153, p=0.015). These data suggests a relationship between intersex severity and declining sperm quality in smallmouth bass from the South Branch of the Potomac River.