Twenty asthmatic patients clinically free of heart disease were studied for the possible arrhythmogenic action of albuterol (salbutamol). Two puffs of either albuterol or placebo were inhaled four times per day on two consecutive days and continuous ECG recordings obtained during each 24-hour period. Sixteen patients had atrial extrasystoles, four with albuterol, one with placebo, and 11 with both drugs. The extrasystoles/hour were 6.55 (23.75 SD) with albuterol and 8.37 (33.82) with placebo, a nonsignificant difference. Ventricular extrasystoles were shown in 11 patients, two with albuterol, two with placebo, and seven during both treatments. The extrasystoles/hour were 2.57 (6.36) and 3.10 (7.61) with albuterol and placebo, respectively. This difference was not significant. These findings suggest that therapeutic doses of albuterol aerosol in asthmatic patients without evidence of heart disease and severe hypoxemia should not be considered a cause of cardiac arrhythmias.