In the early 1980s, the antischistosomal aryl hydantoin Ro 13-3978 (AH01), a close structural analogue of the androgen receptor antagonist nilutamide, was discovered. Administration of 100 mg/kg oral doses of AH01 to mice infected with adult and juvenile Schistosoma mansoni produced 95% and 64% total worm burden reductions, confirming its high activity against adult worms, and showing that AH01 is also effective against juvenile infections. AH01 had no measureable interaction with the androgen receptor in a ligand competition assay, but it did block dihydrotestosterone-induced cell proliferation in an androgen-dependent human prostate cancer cell line. For AH01, nilutamide, and three closely related aryl hydantoin derivatives, there was no correlation between antischistosomal activity and androgen receptor interaction.