Purpose: To determine the prevalence of epilepsy and the role of neurocysticercosis in the occurrence of epilepsy in Atahualpa. Methods: We used a door-to-door survey to detect subjects with epileptic seizures, to collect a blood sample for determination of anticysticercal antibodies, and to evaluate social characteristics of the population, including household pig ownership. Neurologists examined suspected cases and a sample of negative individuals. Then patients with epilepsy, as well as age- and sex-matched controls, underwent a head computed tomography (CT) and a scalp EEG. Results: The questionnaire was answered by 2,415 of 2,548 residents of Atahualpa, and cysticercosis serology was performed in 1,687 consenting individuals. Cysticercosis seroprevalence was 145 (8.6%) per 1,686). Neurologic examination confirmed 24 patients with epilepsy (crude prevalence, 9.9 per 1,000 population, and 10.8 per 1,000 when adjusted to the United States population). After adjustment by age, sex, and pig raising, positive serology was strongly associated with epilepsy (odds ratio (OR), 4.16; 95% confidence interval (CI), 1.6-11.2). CT findings compatible with neurocysticercosis were found in five patients with epilepsy and also were more frequent than in controls, although this did not reach statistical significance (five of 19 vs. one of 19; p = 0.125, McNemar's test). Besides these five cases, three other patients with epilepsy had positive serology (one with a normal CT and two who did not have a CT). Conclusions: Neurocysticercosis is associated with one-third of cases of epilepsy in Atahualpa and may be a major contributory factor for the excess fraction of epilepsy seen in this population. © 2005 International League Against Epilepsy.