A serosurvey for human hydatidosis and cysticercosis was performed in different regions of Peru. Those regions included a known endemic area for cystic hydatid disease, a cooperative in the central Peruvian Andes near the city of Tarma, Department of Junin; three areas endemic for cysticercosis in the Departments of Ancash, Cuzco, and San Martin, where the status of hydatid disease is not well defined; and an urban shantytown near Lima, where neither zoonosis is known to be present. A seroprevalence for hydatidosis 1.9% (6 of 309) was found with both the enzyme-linked immunoelectrotransfer blot (EITB) and double diffusion assays in the area endemic for hydatidosis. Seroprevalence in the other zones tested was zero using only the EITB assay. Cysticercosis sero-prevalence was high in pig-raising zones but low in the high-altitude, sheep raising areas and in the seaport of Callao. No cross- reactions between Echinococcus granulosus and cysticercosis were noted in any of the regions studied. Hydatid infection remains a major health problem in the central Peruvian Andes where sheep raising is widely practiced; however, in those regions where mainly swine are raised, human hydatid infection is not a problem.