Biology and habitat use of mountain whitefish (Prosopium williamsoni)throughout its range are reviewed for its spawning; early developmental, hatching, and emergence; and underyearling, yearling, and subadult to adult feeding and migratory stages. About44%of the 112 relevant publications pertain to U.S. populations (California, Nevada, Utah, Wyoming, Montana, Idaho, Oregon, “Washington), about 42% to British Columbia populations, and the remainder to Alberta or other populations. About 63% of the studies have been published since 1970. There are surprising gaps in essential life history and other biological aspects of the species, which severely limit development of techniques for habitat compensation and improvement arising from impacts on habitat by impoundments, pipeline and road construction, forestry and mining activities, as well as on the populations themselves by recreational fisheries. Nevertheless, a series of specific needs and recommendations for habitat compensation and improvement are given.