GH replacement therapy in GH-deficient adults has recently been shown to increase (normalize) muscle volume and decrease adipose tissue volume as measured by means of CT scan and skinfold thickness. Also in adults with acquired GH deficiency in adulthood, GH replacement has been shown to significantly influence body composition with an increase in lean body mass and a reduction in skinfold thickness. Preliminary results from an open long-term trial indicate that 12 months of GH substitution result in a further normalization of the muscle/fat ratio. The fluid-retaining effect, with a significant increase in extracellular-fluid volume demonstrated during GH administration to normal subjects, seems to be of little clinical importance if a replacement dose around 2 IU/m2/day is chosen for young GH-deficient adults. Long-term trials are needed to finally establish the indication of GH replacement therapy in GH-deficient adults.