SUMMARY Plasma human growth hormone (HGH) concentrations were compared during four tests in which 0·9% NaCl solution only, propranolol, adrenaline or propranolol plus adrenaline were infused into six healthy volunteers. In five subjects, HGH levels during the infusion of saline, propranolol or adrenaline showed no significant increase and were virtually identical. During the test with propranolol plus adrenaline, however, there was an increase after adrenaline in spite of concomitant hyperglycaemia. The sixth volunteer showed a wide range of apparently spontaneous and irregular variations in HGH values throughout each of the four tests. These findings support the view that α-receptors stimulate and β-receptors depress HGH secretion, and show that adrenergically stimulated HGH secretion in man is not inhibited by hyperglycaemia.