ABSTRACTA review of the various genetic, environmental and processing factors which influence the expression of flavor in muscle foods, from animal, avain and aquatic sources, is presented. Special emphasis is given to such variables as species, breed, sex, age, nutrition, primary and further processing operations. Although a variety of factors is known to influence the flavor of muscle foods, no single one or group of factors can be assigned the role of principal influencer. In fresh muscle foods, genetic as well as environmental factors are probably most important. Of the genetic factors, there is little doubt that species exerts the most pronounced effect on flavor. Nutritional effects are the most important of the environmental factors influencing flavor. Primary processing operations (i.e., carcass washing techniques, freezing) can affect the flavor of fresh muscle foods. In further processed muscle foods, the flavor is most affected by those factors which influence product composition.