This study examined the spatial distribution and seasonal fluctuations of population densities of phlebotomine sand flies and was designed to obtain baseline data on the population trends of Phlebotomus argentipes, P. papatasi, and Sergentomyia spp. in a visceral leishmaniasis endemic area of Bihar, India. Beginning on 28 October 2009 and through 20 October 2010, 63 CDC light traps were evenly distributed in human homes, cattle sheds, combined dwellings, chicken coops, and adjacent vegetation areas in three villages in the Saran District of Bihar State. Sand fly collections were made on a weekly basis, sorted, and identified according to species, sex, and feeding status of the two genera. The daily temperatures and relative humidity ranges were collected in a representative human home, cattle shed, and combined dwelling in each of the three study villages. Village census surveys were conducted in the three study villages in February 2010, acquiring human population data, structural composition data, and livestock census information, and documenting the history of visceral leishmaniasis within each household. A total of 52,653 sand flies was trapped and identified over 3,276 trap-nights. Peaks in abundance were observed in November 2009, March and April, June through August. Of the sand flies trapped, 72.1% were P. argentipes, 27.1%Sergentomyia spp., and 0.8%P. papatasi. Distribution of the sand fly captures included 30.6%, 26.7%, 18.6%, 12.1%, and 12.0% from vegetation, combined dwellings, cattle sheds, housing, and poultry houses, respectively.