To our knowledge, ours is the first study to evaluate the outcome of infantile spasms (IS) in adult patients. We analyzed 214 children born between 1960 and 1976 who had been followed for 20-35 years or until death at 3 months to 30 years of age. Mortality was 31% (67 of 214 patients). Thirty-six of the surviving patients (24%) had normal (25 patients) or only slightly impaired (11 patients) intelligence as assessed by their educational abilities. Four had academic occupations. Eight were married or living unmarried with a partner. Five had healthy children. At follow-up, the EEGs of the 25 normal persons were either normal or slightly abnormal, demonstrated focal findings in 9 (36%), and had unspecific changes in 1. Focal abnormalities were not more common in patients with less good outcomes (37%). In patients with normal neurological outcomes, IS had been classified as cryptogenic only in 9 of 25 (36%) cases. Therefore, some patients with IS apparently have normal intelligence and socioeconomic status as adults, including patients whose spasms were either symptomatic or associated with focal EEG findings.