Knowledge of home-range size and subadult dispersal activity of American black bears (Ursus americanus) is essential for understanding the complexity of how bears interact within populations and the environment. During 1993–1998, we monitored 95 radio-collared black bears in the Cascade Range of western Oregon to estimate homerange sizes and dispersal movements. Composite fixed-kernel home ranges were calculated for 37 bears. Mean home-range size differed between genders (189.7 km² for males and 33.6 km² for females); however, there was no difference in mean home-range size between subadult and adult males or subadult and adult females. We monitored 40 subadult bears (29 M, 11 F) to detect dispersal activity. We did not detect any dispersal of subadult females. One subadult male dispersed as a 2 year old, one dispersed as a 3 year old, and one as a 4 year old. The greatest dispersal distance of any subadult was 34 km by a 2-year-old male.