The population abundance of Phlebotomus argentipes Annandale & Brunetti was studied between January 1986 and December 1987 at 2 sites in West Bengal, India, in relation to 8 ecological parameters (air temperature, rainfall, windspeed, relative humidity, soil moisture, soil temperature, soil pH, and soil organic carbon). Sand flies were present throughout the year with minimum abundance in winter months and maximum during monsoon and postmonsoon months. Correlation analysis examined pairwise relationships among the 8 ecological parameters and P. argentipes abundance. Multiple linear regression of sand fly abundance on the 8 parameters showed that average soil temperature and soil moisture, both recorded 1 mo earlier, were associated positively with sand fly abundance. These findings have important implications for Indian kala-azar disease control and prevention. Effective vector management programs are needed most when weather conditions favor increased sand fly abundance, given that greater sand fly abundance increases the likelihood of host-vector contact and the transmission of Leishmania.