Our objectives were to determine which habitat variables had the greatest influence on densities of the Three Forks springsnail (Pyrgulopsis trivialis) and pond snail (Physa gyrina), and to examine interactions between the two species. We measured density and several habitat variables in Three Forks Springs and Boneyard Bog Springs in east-central Arizona. Density of Three Forks springsnails was greatest (500/m²) in shallow water (<5.6 cm), where density of pond snails was less (<4.6/m²), and closer to the springhead (<0.8 m). Density of pond snails was greatest (66/m²) further away from the springhead (≥32 m) and when temperatures were greater (≥15.8°C). Density of pond snails was low (1.1/m²) closer to the springhead (<32 m) when pH was less (<8.4). The two snails apparently partition habitat in response to competition for food or presence of predators.