Acute disseminated encephalomyelitis (ADEM), or acute demyelinating encephalomyelitis, is a rare autoimmune disease marked by a sudden, widespread attack of inflammation in the brain and spinal cord as well as causing the brain and spinal cord to become inflamed. ADEM also attacks the nerves of the central nervous system and damages their myelin insulation, which, as a result, destroys the white matter. It is often triggered by a viral infection or, perhaps exceedingly rarely specific non-routine vaccinations. The present study was conducted in Upgraded Department of Paediatrics, Patna Medical College and Hospital, Patna, Bihar, India. Total 50 cases of the acute disseminated encephalomyelitis (ADEM) were enrolled in the present study. The data generated from the present study concludes that ADEM most commonly present as a polysymptomatic encephalopathy and initially diagnosis may not be clear. Clinical evaluation, MRI & CSF studies are most useful to establish the diagnosis and rule out important differential diagnosis. There is presence of antecedent illness in case of severe presentation. The age, gender, predisposing factor do not influence the outcome, but the severity of presentation influence the outcome at discharge.