In February 1989 we began a combined treatment with mebendazole (3 g/day for 30 days) and praziquantel (1.8 g/day for 15 days) with variable rest periods, in a patients with hydatid disease who had been previously unsuccessful treated only with mebendazole. All the patients were monitored with serological techniques and radiography. Generally the treatment was without side-effects. According to radiography results, there was a reduction in the size of the cyst in 5 patients, in 2 there was no change and 1 patient, the cyst continued to increase in size. Results suggest that the combination of mebendazole more praziquantel could be a pharmacological alternative in the medical treatment of hydatid disease.