(Uploaded by Plazi for the Bat Literature Project) We examined habitat use by bats in the boreal forest of central Saskatchewan during summer 1995 by monitoring echolocation calls across forest types and through the canopy of mature forest. We sampled bat activity in mature aspen (Populus tremuloides)-white spruce t.Picea glauca) mixedwood. aspen. and jack pine (Pinus banksiana) stands and recorded passes from little brown t Mvotis lucifugusv, northern long-eared (M. septentrionalisv, big brown tEptesicus fuscusv or silver-haired bats (Lasionycteris noctivagans), and hoary (Lasiurus cinereuss bats. There were significantly more bat passes per night in the aspen-white spruce mixedwood forest than in aspen or jack pine forest. There was no difference in the proportion of feeding buzzes recorded from aspen-white spruce mixedwood and aspen forest. In aspen forest. mean number of hoary bat calls per night was higher above than below the canopy. whereas number of Myotis calls was higher within and above the canopy than below the canopy. There was no difference in the number of feeding buzzes recorded among the three canopy heights. Bat activity peaked toward sunset below the canopy but was more uniform within and above the canopy. Our results highlight the importance of mature aspen-white spruce rnixedwood and aspen forest as habitat for boreal forest-dwelling bats and demonstrate for the first time that insectivorous bats are active both within and above canopy levels of the boreal forest.