Japanese encephalitis (JE), caused by a mosquito-borne virus was first recognised in India in 1955 and since then many major out-breaks from different parts of the country have been reported, predominantly in rural areas. Children are mainly affected, with morbidity rate estimated at 0.30 to 1.5 per 100,000 population. Case fatality rate has ranged from 10% to 60%, and up to 50% of those who recover may be left with neurological deficits. Reported incidence has generally been higher in males than in females, but subclinical infections have occurred equally in both sexes. A large number of subclinical infections occur each year during the transmission season. Diagnosis at the primary health centre (PHC) level is based on clinical symptoms only. Therefore, there is a need to develop simple tests for use at the peripheral level both for diagnosis and for epidemiological surveys. JE is a vaccine preventable disease, but there are many logistic problems for effective implementation of vaccination.