To investigate natural roost-site selection by eastern red bats (Lasiurus borealis) in an urban area we equipped 12 bats with radio-transmitters and located them at 75 individual roost sites in central Illinois from 16 July to 30 September 1996. Bats used a diversity of roosts including mature trees, leaf litter, dense grass and the shingles of houses, but the majority of roosts (89%) were in the foliage or on the trunks of large deciduous trees (>45 cm dbh). Sweetgum (Liquidambar syraciflua) and oaks (Quercus spp.) were commonly used. Most roosts were located in foliage, >5 m above the ground, within 1.5 m of the edge of the crown and with few branches beneath to obstruct flight paths. Red bats showed fidelity to roost sites within a small geographic area, but not to particular roosts. Individuals rarely used the same roost on consecutive days, but 82% of roosts used on successive days were within 100 m of each other. In the cornbelt region of the Midwest, where forests have been extensively cleared and fragmented, large urban trees provide important roosting habitat for red bats.