Background and Purpose: Epilepsy is highly prevalent in developing African countries with significant morbidity, social stigmatization, poor quality of life and preventable mortality. There are scanty reports on the contributions of seizure variables like seizure types, frequency of seizures, duration of epilepsy, age at onset and anti-epileptic drugs to cognitive disturbances in Nigerian Africans. This study assessed the effects of seizure variables on the cognitive performances of patients with epilepsy. Methods: The cognitive functions of 41 patients with epilepsy and 41 controls were assessed with a computer-assisted cognitive test battery, Iron Psychology (acronym - FePsy) using the simple and complex reaction time tasks for mental speed, recognition memory test (RMT) for memory and continuous performance test for attention. Results: The cognitive performances of the patients using complex reaction time and the recognition memory tasks were worse than those of the controls (p<0.05). The duration of treatment with anti-epileptic drugs negatively affected all cognitive domains assessed. The seizure frequency, duration of epilepsy and the use of phenytoin were associated with psychomotor retardation and impaired memory. Conclusions: The seizure variables negatively affected cognitive performances of Nigerian patients with epilepsy. Cognitive assessment is recommended as part of regular evaluation of patients with epilepsy. © 2002 African Journal of Neurological Sciences. All rights reserved.