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One hundred ten dens of 57 black bears (Ursus americanus) were examined in east-central Ontario from 1976 to 1980. Most bears denned within summer range boundaries. Entry dates ranged from 20 September to 29 November. Denning sequence was yearlings, pregnant females, solitary females, females with cubs, adult males, and subadults of both sexes. Bears that fed on acorns denned later than non-acorn feeders. Eighty-nine percent of dens (N = 110) were excavations below ground level, and 84% occurred on well-drained upland sites. Dens of individual bears in consecutive years were similar. There was no indication of den reuse. Cubs orphaned during the spring hunt constructed and lined dens similar to those of older bears. In 1 instance, a 2-year-old male was denned with an adult female and 2 newborn cubs. Thirty-three percent of yearlings and 11% of subadults abandoned dens due to investigator disturbance; young males abandoned dens more frequently than females. Emergence extended from 23 March to 1 May with a peak around 5-20 April. Males were the 1st group to emerge and females with cubs, the last. Adjustment of hunting seasons to harvest specific sex and age groups selectively during the fall would be only marginally successful due to the lengthy den entrance period and overlap of entrance times among groups. During the spring hunt, females with cubs could be afforded greater protection by closing the hunting season earlier.