Objective: To compare the effectiveness of two regimens of albendazole therapy for neurocysticercosis. Design: Randomized, double-blind clinical trial. Settings: Patients admitted to neurologic wards in Lima, Peru. Patients: Adult patients with active neurocysticercosis demonstrated by CT and Western blot (immunoblot). Intervention: One week (n = 25) versus 2 weeks (n = 25) of albendazole therapy. Measurements: Decrease in the number of cysts on CT. Results: Effectiveness of albendazole was 78%, with no difference between the groups when compared 3 months after therapy. Complete cure was obtained in only 38% of patients. Patients with more than 20 cysts had poorer responses to therapy. The clinical course and EEG evolution improved in most patients. Side effects were present in 38% of patients, mainly mild, transient gastrointestinal symptoms. Therapy was also associated with exacerbation of neurologic symptoms. Two patients died in the first year after therapy, both because of aggregated infections of ventricle-peritoneal shunts. One-year follow-up CT showed lesions in three of 10 patients presumed to be cured 3 months after therapy. Conclusions: Extension of albendazole therapy for more than 7 days adds no benefits for the patients.