Since 1980, visceral leishmaniasis (VL) has reemerged as a public health problem in lowland Nepal. We conducted a case-control study to identify risk factors. In univariate analyses among 84 cases and 105 controls, protective factors included sleeping on a bed or cot (Odds ratio [OR] 0.44, P < 0.01) and sleeping under a bed-net regularly (OR 0.23, P < 0.001) or in the warm months (OR 0.20, P < 0.001). The bed-nets in use in this region were commercially available and untreated with insecticide. Ownership of a cow or buffalo was protective (OR 0.34, P < 0.001), whereas dampness observed in the mud floor of the house was a strong risk factor (OR 4.0, P < 0.001). In multivariable models, bed-net usage, cow or buffalo ownership, and damp floors were significantly associated with altered risk. A program to increase bed-net usage could therefore decrease the incidence of VL in Nepal.