Isoproterenol and propranolol, in a single dose, caused hyperglycemia after 15 and 30 min, either in the conscious rat or in the anesthetized dog. In this latter species no modifications of the serum potassium were observed. Adrenaline, 5 microgram/kg, iv provoked hyperglycemia at the same intervals and hyperkalemia at min 1st and 2nd with further hypokalemia until 90 min. The beta-adrenergic blocker, sotalol, 5 mg/kg, iv, administered prior to adrenaline suppressed the increase in glycemia and the late decrease in serum potassium, but not the early hyperkalemia. In the isolated hind limb of the dog the intra femoral artery administration of adrenaline, 3 microgram/kg, produced similar hyperglycemia either in the artery or in the femoral vein, starting from the 15 min. Contrarily, the serum concentration of potassium was significantly less in the vein than in the artery at the 1st min. These findings suggest that different receptors are involved in the glucose and potassium response to adrenaline, and the skeletal muscle plays an important role in the regulation of the early hyperkalemia.