Abstract To investigate the possible etiologic factors of late onset seizures of unknown origin, 50 consecutive patients whose seizures started after age 50 and who had a normal CT, were screened. The seizures in this group were generalized in 70% and infrequent. The hypothesis that late-onset seizures of unknown origin were frequently due to microinfarcts, was evaluated by comparing the frequency of arterial hypertension, coronary heart disease, peripheral vascular disease, carotid bruits, diabetes mellitus and smoking in these patients with appropriate control groups. The results showed that the frequencies of these cardiovascular risk factors were similar to those of sex and age-matched controls and much lower than in a comparable series of patients whose seizures followed a stroke, or patients with stroke but no seizures. These data suggest that subclinical cerebrovascular disease is probably not a frequent etiology of late-onset epilepsy of unknown origin. The cause of these seizures remains to be elucidated.