Door to door search during 1991 in 85 villages in Ballia district of Uttar Pradesh revealed 29 sporadic cases of Kala-azar in four villages. Epidemiological investigations indicated indigenous transmission in Phulwaria village (PHC: Dubhar) with 25 cases while the remaining three villages showed four imported cases from the endemic states. No kala-azar cases had been reported in Ballia between 1947 and the present investigation. Phlebotomus arqentipes, the known vector of kala-azar in India, was encountered in 10 PHCs including the four villages having kala-azar cases. Regular vigilance in Ballia and the neighbouring districts in Uttar Pradesh bordering Bihar is suggested in view of indigenous transmission detected in one village with multiple infection in families. The presence of high vector density, ambient environmental factors and absence of regular residual insecticidal spray warrant constant surveillance in Kala-Azar prone areas in Uttar Pradesh.