SUMMARY The administration of 5 mg. ovine growth hormone (GH) per day for 4 weeks to adult sheep resulted in the retention of 0·5 g. nitrogen/24 hr. This is less than that reported to occur in man and dog with a similar dose of GH. Both plasma volume and red blood cell volume increased by 20 % during treatment. A small decrease occurred in the amount of sodium excreted, but no change in potassium excretion could be demonstrated. The water intake of the treated group declined during GH injections. Plasma glucose concentrations increased slightly during treatment but there was no alteration in the concentration of plasma free fatty acids or ketone bodies. Body weight did not change measurably with GH treatment. Wool growth decreased during treatment but then increased and remained above control values for at least 20 weeks.