Three parenteral routes of albuterol sulfate were compared with placebo in their effects on serum potassium and glucose levels, heart rate, and pulmonary function in adult asthmatic subjects. In addition, the metabolic effects of subcutaneous epinephrine were compared directly with subcutaneous albuterol. Intravenous (IV) albuterol (250 micrograms) caused similar decreases in serum potassium (mean 0.6 +/- 0.3 mEq/L) as 500 micrograms albuterol by intramuscular (IM) or subcutaneous routes. With the combined data from all three albuterol routes, glucose increases (mean 25 +/- 15 mg/dl) and heart rate increases (mean 11 +/- 6 beats/min) were clinically less important than potassium decreases. Subcutaneous epinephrine (0.3 ml, 1:1,000) gave changes in serum potassium, serum glucose, and heart rate statistically similar to those of subcutaneous albuterol (500 micrograms). Peak FEV1 improvement (mean 61 percent) was similar with IV albuterol (250 micrograms), IM albuterol (500 micrograms) or subcutaneous albuterol (500 micrograms). Although the efficacy of albuterol in the doses studied was similar, the decrement in serum K+ produced was also similar and comparable to that produced by a standard dose of epinephrine. The potassium decrease may have important clinical implications.