The Taenia solium taeniasis/cysticercosis complex is an important public-health problem in several countries, where many epileptic seizures appear to be associated with neurocysticercosis. As few data on this problem in Nicaragua exist, the seroprevalence of antibodies reacting with antigens from T. solium cysticerci was investigated among 88 Nicaraguan epileptics (45 males and 43 females, aged 6-53 years). In questionnaire-based interviews, each adult subject and a caregiver of each child investigated were asked about potential risk factors for taeniasis/cysticercosis. When a serum sample from each subject was then checked for anti-cysticercus antibodies, 8.0% of the subjects were found seropositive by ELISA and 14.8% by western blotting. Five samples (all from individuals who had been epileptic for > 5 years) were positive in both tests. When the level of association between each potential risk factor and seropositivity (in ELISA or by blotting) was evaluated, the only statistically significant association detected was that between a positive ELISA and the subject living in a household where pigs were raised (odds ratio = 5.18; 95% confidence interval = 0.8-41.6; P = 0.05). The bands most frequently recognized in the western blots (of 50, 42-39, 24 and 14 kDa) were those previously reported. The results indicate that, in the city of Léon, cysticercosis may be endemic and the cause of a significant proportion of the epilepsy recorded.