The exact prevalence of epileptic seizures in patients with multiple sclerosis (MS) is still a matter of some controversy. In a population-based, unselected group of 423 patients with MS we identified 17 (4.02%) with epileptic seizures. The mean age at onset of MS was 25.2 years and at onset of epilepsy 32.6 years. A prevalence of 'active epilepsy', i.e. seizures within the last 5 years, was estimated to 3.2%. The prevalence of epilepsy in our MS population is much higher than should be expected when compared to lifetime prevalence of epilepsy in corresponding age groups. The occurrence of convulsive status epilepticus is also higher than expected, and suggests a rather serious prognosis. Thus, drug treatment should be considered after the first epileptic seizure.