In a randomized, double-blind, two-way crossover study in four centers, 124 patients received single doses of 4 or 6 mg of albuterol and placebo on two separate visits. Pulmonary function tests were performed at intervals up to ten hours. Both dosages produced peak bronchodilation responses which occurred at two hours and significant activity was maintained for at least eight hours. Adverse experiences were typical of adrenergic agents.