By examining the sera from 1,408 healthy individuals in all six provinces of Madagascar with ELISA methods, we were able to demonstrate a very high prevalence for cysticercosis: 18%. The serologic markers for cysticercosis among 1,132 patients with neurologic symptoms was even higher: 36%. Furthermore, of 241 patients with neurocysticercosis, 82% of the serums recognized, in Western Blot test, the 14-20 Kd "evolutivity proteins". Cysticercosis is thus highly implicated in the neurologic syndromes found in Madagascar. Only adequate prophylaxis will permit a reduction in the incidence of this disease.