Although long-term follow-up data are available for cases with acute disseminated encephalomyelitis, the findings range widely because of the lack of consistent definitions. Using the International Pediatric Multiple Sclerosis Study Group definitions strictly, we determined the long-term prognosis of children with acute disseminated encephalomyelitis, especially concerning relapsing cases. In our cohort of 86 children who presented with a first event of inflammatory demyelinating disease of central nervous system, 33 patients (38%) met the Study Group criteria for acute disseminated encephalomyelitis of which 9 patients had relapses. The mean follow-up duration was 12.8 years for relapsing cases and 9.2 years for all patients with acute disseminated encephalomyelitis. The risk of developing relapses is 27% but the risk of developing multiple sclerosis from acute disseminated encephalomyelitis is low at 6%. All relapsing cases had a benign course on prolonged follow-up, in spite of multiple relapses in the first 3 years.