An investigation in the Selway-Bitterroot Wilderness of north-central Idaho helped evaluate the effects of fire on marten (Martes Americana) habitat and food sources. Voles (Microtinae) were the most abundant item in the marten diet, occurring in 79 percent of 129 marten scats. These were most abundant in mesic habitats. A total of 2,896 trap days during November 1973 through March 1974 and November and December 1974 resulted in 80 captures of 13 marten and 255 track observations. Marten used a variety of forest types. The highest activity when snow depths were normal was in stands having an Englemann spruce/subalpine fir (Picea engelmanni/Abies lasiocarpa) overstory, canopy cover greater than 30 percent, mesic habitat type, and an overstory age greater than 100 years. The effects of fire on marten habitat and foods are discussed.