Bat conservation is hindered by a lack of geographic-specific knowledge of characteristics of roost sites used by reproductive females. We examined roost selection by reproductive female Myotis evotis (long-eared myotis) in the Channeled Scablands of northeastern Washington. We used radiotelemetry to locate 35 roosts of reproductive female Myotis evotis. Habitat variables were measured for each roost itself and at a 0.1-ha microplot and 78-ha macroplot surrounding each roost. We measured habitat variables at random 0.1-ha microplots in the vicinity of each roost and at general random 0.1-ha microplots and 78-ha macroplots. Thirty-four roosts were found in crevices in small basalt rock formations. All radiomarked bats switched roosts at least once and roost switching apparently involved the entire colony. The average number of switches was 3.3 with an average of 2 days between roost switches. The distance traveled between day roosts averaged 148.9 m. Compared to random plots, roosts were in more open, rocky habitats, closer to edge of forest stands, and relatively distant from sources of permanent water.