Four children with chronic, mild, nonspecific symptoms are described in whom magnetic resonance imaging (MRI) showed the presence of multifocal white-matter lesions suggestive of acute disseminated encephalomyelitis. The children ranged in age from 14 months to 15 years. The clinical picture was vague and inconclusive and consisted of several months of headaches, irritability, clumsiness, and personality change. Physical examinations were noncontributory. Laboratory investigation revealed no other cause of the demyelination. All of the patients have done well without any treatment, with a disappearance of symptomatology. The white-matter lesions on MRI scan in these children may indicate subtle exposure to a myelinolytic antigen. It has been suggested that such an exposure may create a state of complete or partial resistance to the encephalitogenic potential of the next infection or immunization. With complete resistance, the patient remains healthy and with partial resistance progressive demyelination results. Verification of these findings by others would suggest a possible benefit of a multicenter study of such patients, with virological, HLA testing, and long-term follow-up, in understanding the etiopathogenesis of multiple sclerosis. (J Child Neurol 1989;4:213-216).