Hand tremor, heart rate and electrolyte, plasma (pl) insulin, blood (bl), glucose, and pl terbutaline levels were measured in 11 healthy men during infusion and oral administration of terbutaline [a sympathomimetic drug used in the treatment of bronchial asthma]. Infusion of terbutaline (250 .mu.g) was followed by increases in pl insulin concentration and bl glucose and by a decrease in pl K. Similar metabolic changes were seen on day 1 of oral terbutaline (5 mg .times. 3). Heart rate was moderately increased by terbutaline over the entire period (13 days) of oral dosing. Hand tremor always increased after terbutaline, but to a lesser degree on days 4 and 13 than after the 1st oral dose. On day 13 there was a very small increase in pl insulin and no reduction in pl K; bl glucose increased slightly from an elevated basal level. Pl terbutaline was of similar maximum concentrations on days 1 and 13, indicating that the tolerance was mediated through reduced response of the effector organs.