We report characteristics of maternity roosts of Allen's lappet-browed bat (Idionycteris phyllotis) at the northernmost extent of its range. In summer 2004, three female I. phyllotis were fitted with radiotransmitters and followed to three roosts in cracks of the same cliff face within Grand Staircase-Escalante National Monument, Kane and Garfield counties, Utah. There were ≥15 bats in the three roosts, which were on a large northwest-facing cliff, in the eastern side of a small box-canyon. Piñon-juniper (Pinus-Juniperus) woodland was on ridge tops and bottoms of canyons, which were ca. 1,800 m elevation with mature to old-growth woodlands. Roosts were in the top one-half of the cliff face, which was tall and highly fractured, with a large talus slope at the base.