The authors tried piperazine plus thiabendazole for the treatment of Ascaris lumbricoides and hookworn infections. The drug was given for 2 consecutive days in a daily dose of 750 mg of piperazine hydrate and 375 mg of thiabendazole for 33 kg of body weight. Cure was obtained in 81% of those infected with A. lumbricoides and in 80% of hookworm infections. Tolerance to the drug was considered very good.