In a series of 2,353 multiple sclerosis (MS) patients, 40 subjects presented seizures, with an overall prevalence of 1.70%. The prevalence was 2.33% (34/1,459) in definite MS cases, 0.58 in probable cases (3/518), 0.79 in possible cases (3/376). Twenty-six patients were females, 14 were males. In 13 cases, epilepsy had begun before MS onset; in 4 patients, the two diseases started contemporarily; in 23 patients, epilepsy followed MS onset. No relationship was found between frequency of seizures and course of MS nor between frequency of seizures and MS severity. In 12 patients, magnetic resonance imaging was performed: plaques adjacent to the cerebral cortex were found in 3 cases. The electroencephalogram showed paroxysmal discharges in 11 patients (focal in 2, diffuse in 9). Slow theta and/or delta activity was found in 15 patients (focal in 7, diffuse in 6, both focal and diffuse in 2). The EEG was normal in 14 patients. Possible etiological factors other than MS were recognized in 4 patients only: cranial trauma in 3, meningitis in 1. Our study on a large MS population confirms that MS is associated to a risk for epilepsy higher than that of the general population.