The metabolic and cardiovascular side-effects of intravenous infusions of therapeutic doses of beta 2-adrenoceptor agonists salbutamol and rimiterol have been determined in four healthy male subjects. There were dose-related increases in plasma glucose, renin activity, serum insulin and heart rate, and significant hyperlactataemia and ketonaemia. There were dose-related decreases in plasma potassium, phosphate and corticosteroids and significant hypocalcaemia and hypomagnesaemia. The effects of equivalent molar amounts of salbutamol and rimiterol were similar. Whichever drug is used, special care is required with patients who may have abnormal glucose tolerance, potassium depletion, or be predisposed to lactic acidosis. Rimiterol may be preferable for infusion because of its short plasma half-life.