Growth hormone deficiency in adults is associated with psychosocial maladjustment, reduced muscle strength, and reduced exercise capacity. Body composition is significantly altered, with increased fat and decreased muscle volume as compared with healthy subjects. Kidney function is subnormal. Epidemiological data suggest premature mortality owing to cardiovascular disease in hypopituitary patients. Short-term GH treatment trials have shown improved psychosocial performance, normalization of body composition, increased muscle strength, improved exercise capacity, increased cardiac performance, and normalization of kidney function. Thus GH replacement therapy in GH-deficient adults exhibits potential long-term beneficial effects. A number of important questions have to be addressed before long-term GH replacement therapy in GH-deficient adults can be considered on a routine basis.