The secretion of both growth hormone (GH) and androgens declines with age which may play a role in the senescent changes in body composition and organ function. Among healthy adults abdominal adiposity is an important negative determinant of GH secretion. Surprisingly, abdominal or android obesity seems inversely correlated with testosterone levels in males but not in females. The ability of GH to promote lipolysis and preserve or increase lean body mass has been reappraised in substitution studies in GH-deficient adults. By comparison, adequately controlled studies of androgen replacement in hypogonadal and/or elderly males are few. In view of the physiological and clinical relevance of obtaining information about the aging process, there is a need for controlled experiments addressing similarities and differences between the action of GH and sex steroids in adults.