Among the viral encephalitides that are encountered in our country. Japanese encephalitis (JE) appears to be of greater significance than the others. This disease, which is caused by an ar thropod borne (ARBO) R N A virus known as Japanese encephalitis virus, is also prevalent in many parts of the world. It appeared in an epidemic form in Japan, China, Korea, 1 USSR, 2 and in many other South East Asian countries. In India a small outbreak of JE among children was observed for the first time in and around Vellore in the North Arcot District of Tamil Nada.Z Since then it has been a public health problem along the east coast of India, which includes the Krishna-Godavari delta, West Bengal, the foot hills of NEFA and the Brahmaputra valley in Assam. For nearly the last two decades. there have been sporadic cases and smaller outbreaks of JE in different parts of the country, except in the West and the North West. In 1973, this disease for the first time reached aa epidemic propor t ion in Bankura and the Burdwan Districts of West Bengal. 4 Subsequently, in the years 1977 and 1978, a locallsed out-