Acute encephalitis syndrome (AES) is a term used by WHO for syndromic surveillance in the context of Japanese encephalitis (JE). Encephalitis is inflammation of the brain. Severity is variable. Symptoms may include headache, fever, confusion, a stiff neck, and vomiting. The present study is carried out with the objective to evaluate the clinico-demographic profile of hospitalized paediatric AES cases to determine the incidence and outcome of acute encephalitis syndrome to document the outcome of the study in relation to the clinical profile of the enrolled subjects. The data from the 50 patients were collected and presented as below. All the patients were undergone CSF analysis, Fundus examination, Monteux test, Chest X - ray, CT Brain, MRI Brain, EEG, Virological studies. Hence from the abode study it can be concluded that AES major cause of mortality in children in this region of Bihar. Even though vaccination has been incorporated in the National Immunization Schedule in these endemic regions, vaccination rates and efficacy are still low.