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We studied 21 brown bear (Ursus arctos) dens in the mountains of the northeast Brenta range in Trentino, Italy. Of these, 2 dens were located during the late 1970s using radio-tracking, 1 den was located in 1989 by a different researcher, and 18 dens were located by the authors between 1988 and 1994. Two dens were excavated and 19 were in natural cavities. Bedding material in these dens consisted of nest-like beds (n = 15 dens), a hole dug in the earth (n = 2), bedding materials spread out on the ground (n = 3), and no bed in 1 excavated den. Nine dens showed signs of recent use. To determine factors bears use to select a hibernation site, characteristics (e.g., elevation, exposure, slope angle, and distance from sources of disturbance) were noted for 19 dens located in the area where bears are constantly present and compared with the same characteristics taken from 100 uniformly distributed sites in the same area. Elevation of the den sites ranged between 970-1940 m. The angle of the slopes on which the dens were located ranged between 28°-60°. Brown bears preferred den sites with southern exposure over those with a northern exposure and used slopes facing all cardinal compass directions.