A study was undertaken to compare the efficacy of three drugs in the treatment of uncomplicated strongyloidiasis in Okinawa, Japan. Two hundred and eleven patients with confirmed Strongyloides stercoralis infection were given either ivermectin, 6 mg in a single dose, albendazole, 400 mg/day for 3 days or pyrvinium pamoate, 5 mg/kg/day for 3 days. For each treatment, the same regimen was repeated once 2 weeks later. Efficacy was evaluated at 2 weeks, 6 months and 12 months after the second course of treatment. Each follow-up examination included a parasitological examination of z stool specimens, using the agar-plate culture method. Coprological cure was obtained in 65 of the 67 patients treated with ivermectin (97.0%), in 65 of the 84 patients treated with albendazole (77.4%) and only in 14 of the 60 patients who were given pyrvinium pamoate (23.3%). The cure rates were lower in males and in the patients with concurrent HTLV-1 infection. An epidemiological feature of Strongyloides infection in recent Okinawa might allow workers to evaluate the exact efficacy of the treatment for an extended period, over a year, without the possibility of reinfection from the environment.