The aims of the study were to describe the prevalence and characteristics of epilepsy in a population of patients with cerebral palsy in a university referral center and to determine the rate of relapse caused by discontinuation of antiepileptic drugs after a 3-year seizure-free period. A total of 178 consecutive patients with cerebral palsy and epilepsy were prospectively followed for 9.2 +/- 2.4 years after onset of seizures and compared to a control group of 150 epileptic patients without cerebral palsy (median follow-up period, 10.5 years). The overall prevalence of epilepsy was 36.1%. Patients with atonic-diplegic, dystonic, tetraplegic, and hemiplegic cerebral palsy had a higher incidence of epilepsy (87.5%, 87.1%, 56.5%, and 42%, respectively). In all, 134 (75.3%) patients were seizure free for more than 3 years and could discontinue therapy, whereas 44 patients (24.7%) were still on antiepileptic drugs. Eighteen of 134 patients relapsed after a 3-year seizure-free period and subsequent discontinuation of antiepileptic drugs, thus giving a relapse rate of 13.4%. First seizures occurred during the first year of life in 69.7% of the patients with epilepsy and cerebral palsy. Complete control of seizures could be achieved in 65.2% of the patients with cerebral palsy and epilepsy; however, regardless of the prognosis of seizures, epilepsy was a major prognostic factor regarding both the presence of mental retardation and the motor development of children with cerebral palsy.