From 1963 to 1972 39% of 251 fawns born in a captive herd of white-tailed deer (Odocoileus virginianus) died with signs attributable to strongyloidosis. At necropsy one typically affected fawn contained 50,000 female Strongyloides in its small intestine. These nematodes and free-living adult females cultured from feces compared morphologically and metrically to S. papillosus. Egg counts on infected fawns varied from 200 to 286,000 eggs per gram of feces. Evidence was obtained that intrauterine transmission of this parasite occurred. The disease was controlled by removing fawns from their mothers shortly after birth and raising them on bottled milk and out of contact with the ground. Fawns were treated with thiabendazole at 6 and at 30-40 days of age and maintained in pens with elevated wooden floors until 8-10 months of age. The original source of the Strongyloides infection in this captive herd and the possible significance of this disease in wild populations of deer are discussed.