The prevalence of epilepsy in children and adolescents from birth through age 19 years was determined for residents of two counties in central Oklahoma. Cases, identified from hospitals, clinics, private physicians' offices, and EEG laboratory and emergency room records, numbered 1,159, yielding a prevalence rate of 4.71 per 1,000. The prevalence was highest in children aged 1-4 years. Overall, males had a slightly higher prevalence rate than females (M:F = 1.1). However, the male/female ratio varied by age, with the group aged less than 1 year having the highest ratio (M:F = 1.5), and by type of epilepsy, with males having higher rates of simple partial epilepsy (M:F = 1.8) and infantile spasms (M:F = 1.5). The prevalence of epilepsy was higher in blacks than in whites. Differences in prevalence by race were confined primarily to generalized epilepsies (B:W = 1.8). The most common types of epilepsy were tonic, clonic, and tonic-clonic (1.14 per 1,000), complex partial (0.39 per 1,000), and partial seizures secondarily generalized (0.33 per 1,000). Approximately 70% of cases were considered idiopathic. Among the presumed causes were perinatal factors (7%), trauma (4%), central nervous system (CNS) infection (3%), and congenital/developmental factors (3). Sixty-five percent of cases had at least one additional medical problem. The most common types of comorbidity were motor handicap (13%) and developmental delay (24%).