Background: A study was conducted in VIMS hospital at Bellary during the epidemic of August 2004 to July 2005. Objectives: To know the association of Japanese encephalitis occurrence with epidemiological factors. Materials and methods: 82 children admitted to the Paediatric ward, VIMS, Bellary with clinical diagnosis of acute viral encephalitis, during the epidemic of August 2004 to July 2005 were studied. After pooling the samples, they were subjected to J.E. MAC ELISA. The association of epidemiological factors with both suspected cases as well as the positive cases was studied. Results: In this study the role of epidemiological features involved in J.E. is well documented. Both the suspected patients as well as the serologically confirmed cases of Japanese encephalitis were more associated with living in rural areas with unhygienic living conditions. Many of them were from the low socio economic group. More number of J.E. cases and flaviviral infections occurred in the rainy season followed by in the winter season. Conclusion: J.E. is the most common form of sporadic and epidemic encephalitis in the tropical regions and should be ruled out first before considering the other viral causes. Illiteracy, low socio economic status and living in unhygienic conditions near rice fields contributed to the high incidence of J.E. in and around Bellary. Residents in endemic areas should take personal protection to reduce the number of mosquito bites. The peak incidence of J.E. is seen from October to December which is the post monsoon period in the area of study.