Neurocysticercosis is the main cause of acquired epilepsy in developing countries and is an emerging disease in the United States. Introduction of the immunoblot assay provided a new tool for the diagnosis and monitoring of neurocysticercosis. This study analyzed the relationship between clinical characteristics of cerebral infection (number and type of lesions) plus the baseline response on immunoblot and the changes observed after therapy. Reaction to all 7 diagnostic bands was associated with severe infection (more lesions). Seventeen patients (35%) had no active lesions on computed tomography (CT) 3 months after therapy and were considered cured. Although most cured patients remained seropositive after 1 year, 3 became seronegative before 9 months. In these 3 cases, the lesions had resolved on CT at 3 months. Persistent seropositivity does not necessarily indicate active infection. Serologic follow-up will be clinically helpful only in rare cases in which early antibody disappearance occurs.