Fifty-seven cases satisfying criteria of the diagnosis of acute viral encephalitis were studied. They were divided into two groups: Group 1 (presumed), 48 cases; Group 2 (postinfectious), nine cases. A possible association of viral aetiology was found in 26%. Viruses isolated were: influenza (3 cases), Coxsackie virus (2), adenovirus (2), mixed cytomegalovirus and adenovirus and herpes simplex viruses (1 case each). The mortality rate was 28%. Among the 41 survivors, 76% were completely normal and 24% had neurological sequelae with focal neurological deficit in 29%; personality changes in 6%; moderate mental retardation in 2%; severe mental retardation in 4%; hyperactivity in 4% and epilepsy in 4%. The best predictors to unfavourable outcome were the rapid rate of deterioration in conscious level after admission and the age of the patients.