Female mice treated with dehydroepiandrosterone sulfate early during infection were partially protected (P < 0.05-0.005) from Schistosoma mansoni infection. Hormone treatment did not modify parasite-specific cellular or humoral responses. Serum dehydroepiandrosterone sulfate levels and testosterone infection were negatively correlated, r = -0.621 and r = -0.653, respectively, with schistosome worm burden. The partial resistance to schistosome infection in dehydroepiandrosterone sulfate-treated female mice may be due to the known antischistosomular activity of testosterone.