Body composition has become a major field of interest for many exercise and sport scientists as well as clinicians who specialize in the prevention of and rehabilitation from hypokinetic diseases. This paper discusses the state of the art within selected areas of body composition, identifying significant areas of controversy and proposing specific problems where research should be focused. The areas addressed include the following: the use of body density to estimate relative body fat in selected populations, the use of anthropometric equations to estimate body composition, body composition assessment for profiling and counseling athletes, and alterations in appetite and body composition resulting from acute bouts of exercise and from exercise training.