Fifteen patients with inoperable hydatid disease (Echinococcus granulosus) were treated with an initial 6-week high-dose mebendazole regimen with a follow-up ranging from 3-7 years. Ten of 15 patients showed both objective and clinical improvement, although two of these 10 relapsed 1-6 years after completing therapy. Simple, single cysts in the lung and liver showed the best response. Multiple, complex cysts and bone cysts showed little or no objective improvement. One patient developed reversible neutropenia. Overall results were no better than those obtained by others with smaller doses.