The fisher (Martes pennanti) is a forest mustelid that historically occurred in California from the mixed conifer forests of the north coast, east to the southern Cascades, and south throughout the Sierra Nevada. Today fishers in California occur only in 2 disjunct populations in the northwestern mountains and the southern Sierra Nevada. We studied the ecology of fishers in both populations (the north coast [Coastal] and southern Sierra Nevada [Sierra]) to characterize the size and composition of their home ranges, and to compare features between locations. Twenty-one (9 Coastal, 12 Sierra) of 46 radiocollared fishers were relocated frequently enough (>20 times) to estimate home ranges. The home ranges of males (X̄ = 3,934.5 ha) were significantly greater than those of females (980.5 ha), and the home ranges of females were significantly greater in the Coastal than in the Sierra area. The smaller home ranges in the Sierra were probably due to productive habitats rich in black oak (Quercus kelloggii). Midseral Douglas-fir (Pseudotsuga menziesii) and white fir (Abies concolor) types composed the greatest proportion (42.8%) of home ranges in the Coastal study area. The greatest proportion of home ranges in the Sierra study area were in the intermediate tree size class (60.7%), had dense canopy closure (66.3%), and were in the Sierran Mixed Conifer type (40.1%). These measures provide guidelines for managers who wish to influence landscape features to resemble occupied fisher habitat. The recovery of fishers in the Pacific States, however, will also require the consideration of microhabitat elements and characteristics of landscapes that might affect metapopulation dynamics.