Adult patients suffering from acute asthma presenting to the Emergency Department with an FEV1 of less than 40% of predicted were randomized into four treatment groups. They were treated with nebulized albuterol at a high (7.5 mg) or standard (2.5 mg) dose given either continuously through 1 h, or intermittently every hour, for 2 h. When the FEV1 improvements for the different groups at 2 h were compared, the groups treated with continuous nebulization had the greatest improvement. The improvements (1.07 L for the high-dose group, and 1.02 L for the standard-dose group) were significantly greater than the improvement seen with standard-dose intermittent treatment (0.72 L; p < 0.05). The improvement in FEV1 of the high-dose, hourly treated group was intermediate in magnitude between these (0.09 L). There was no difference in the improvement seen between the two groups treated with continuous nebulization. The potassium fall, present in all groups, was more pronounced in the groups treated with high doses of albuterol. Only one person (high dose, continuous treatment group) developed hypokalemia of less than 3.0 mmol/L. The high-dose hourly treated group had the highest incidence of side effects, and the standard-dose continuously treated group had the lowest. The standard-dose continuous-treatment regimen had the greatest improvement in FEV1 with the least number of side effects.