To study the feasibility of using high-dose continuously aerosolized albuterol aerosol in adults, seven adult asthmatic patients were treated eight times with 0.4 mg/kg/h albuterol delivered by continuous nebulization over 4 h. One patient withdrew at 3 h after supraventricular tachycardia developed. This subsided promptly on discontinuing albuterol therapy. Heart rate increases were observed in six of eight treatments and serum albuterol levels at the end of treatment were greater than 25.0 ng/ml in all but one treatment. A mean increase in heart rate of 16.3 percent was observed for the entire group. Of the treatments with elevated (> 25.0 ng/ml) serum albuterol levels, a significant cumulative increase in heart rate was observed with time. A significant improvement of FEV1 was observed (p = 0.0025) with a net increase of 36.8 percent. These data suggest that high-dose continuously aerosolized albuterol treatment in some adult asthmatics can result in markedly elevated serum albuterol levels and potential cardiac stimulation despite spirometric improvement.