Taenia solium cysticercosis is an important public health problem in developing countries. Oxfendazole has been shown to be highly effective against porcine cysticercosis, when given as a single dose at 30 mg/kg bodyweight. This dose, however, was estimated from experience with albendazole. A controlled dose-response trial was therefore undertaken to determine the efficacy and safety of three concentrations of oxfendazole. Twenty-four naturally parasitised pigs were divided into four groups and treated with oxfendazole at 10 mg/kg, 20 mg/kg or 30 mg/kg, or left untreated. Eight to 10 weeks later the pigs were killed and the viability of the parasites assessed by evagination. No side-effects of oxfendazole treatment were observed. In the control group more than 90 per cent of the cysts were viable. Viable cysts were found in the muscle and brain of the pigs treated with 10 or 20 mg/kg oxfendazole. At 30 mg/kg there were no viable cysts in any of the tissues examined, indicating that this concentration of oxfendazole provided an effective treatment against porcine cysticercosis.