We report auxologic data on 23 males with idiopathic hypopituitarism who grew up at a time when human growth hormone (GH) was not yet available, while receiving other appropriate hormonal substitution. We had reported previously that their adult heights were not significantly less than those of similar patients who had received GH. In the absence of GH the pubertal growth period was remarkably protracted, averaging 8.7 years for 19 patients during androgen substitution. Pubertal increment in height averaged 20.4 cm during induced puberty, a figure which compares favourably with those reported for GH-treated patients. This implies that GH does not increase the height gained during pubertal growth; the increase in the rate of growth appears to be off-set by a rise in the rate of skeletal maturation. During pubertal growth acceleration of growth of the skeleton seems unavoidably associated with acceleration of its maturation. Adult heights were significantly correlated with the heights at the time of onset of pubertal growth. This is evidence in favour of attempts to stimulate prepubertal growth much more than hitherto by earlier, higher, and more frequent doses of GH. It remains to be proved, however, that before puberty the processes of growth and maturation of the skeleton can be dissociated.