The recent spread of the swim bladder nematode parasite, Anguillicola crassus, in American eels (Anguilla rostrata) along the Atlantic coast has caused concern among biologists and fishery managers. This study documented the presence of A. crassus in yellow-phase American eels on the Shenandoah River, West Virginia. Two hundred eels were collected at Millville Dam during fall 2006 and summer 2007. Swim bladders were removed and examined for the presence of the adult nematode parasite. The number of adult parasites in each eel was recorded, and prevalence (percent of infected eels), intensity (number of nematodes per infected host), and mean intensity (average number of nematodes per infected host in a sample of hosts) were calculated. We plan to measure the relationship between length and age to parasite infestation rate. This is the first study that confirms the presence of A. crassus in the upper freshwater portion of the Potomac River watershed.