Mosquitoes are vectors for many important diseases. Being a vector means that it carries a disease from one host to another. Many of these diseases have a distribution, high, and a high number of cases but some do not, Japanese Encephalitis is also one of the diseases transmitted by mosquito vector. JEV has been isolated from ten species of the genus Culex, three species of Anopheles and three species of Mansonia in India. Of these the largest numbers of isolates have come from two species. Culex tritaeniorhyn and Cx vishnui are incriminated as major vectors in Southern India. By large in whole of South East Asia and India, maximum number of JEV isola-tion have been done from members of Culex vishnui group of mosquitoes which include three species i.e.. Cx. tritaeniarhynchus Giles, Cx. vishnui Theobald and Cx. pseudovishnui Colless.