Between 1986 and 1988, 34 patients (age range six to 83 years) with visceral or ocular larva migrans were randomly assigned to a five-day treatment with thiabendazole 2 x 25 mg kg-1 day-1 (15 patients) or albendazole 2 x 5 mg kg-1 day-1 (19 patients). On the fifth treatment day, six patients (40%) in the thiabendazole group and 11 patients (58%) in the albendazole group showed excellent or good drug tolerability. Efficacy of treatment was assessed after 30 weeks (range six to 56 weeks). In the thiabendazole group, median eosinophilia remained at 14% and four patients (27%) were clinically cured. In the albendazole group, the median eosinophilia decreased from 10 to 3.5% and six patients (32%) were clinically cured. We recommend albendazole for treatment of visceral and ocular larva migrans with a minimum dose of 10 mg kg-1 daily for five days.