The Ozark big-eared bat (Corynorhinus townsendii ingens) is an endangered subspecies currently known only from small populations in Arkansas and Oklahoma. Between October 1998 and May 2000 we surveyed 93 small caves in northwestern Arkansas six times. During these surveys we encountered Ozark big-eared bats in 8–10 caves every season. During surveys in spring, summer and autumn, we encountered mainly lone individuals, while up to seven individuals were encountered together during winter surveys. Winter encounters were mainly in limestone caves, particularly those with vertical or near vertical sinkhole entrances, whereas caves with more varied characteristics were used in other seasons. Temperature may also have been a factor in choice of caves, with colder caves being preferred, especially in winter. Our data indicate that Ozark big-eared bats use many small caves in the study area. These caves should be protected, and other groups of small caves in the Ozarks should be surveyed for Ozark big-eared bats.