Conflicting reports have appeared concerning the role of anticholinergic agents in the treatment of acute asthma. This study was designed to determine whether atropine sulfate, the only anticholinergic agent currently available in the United States for nebulization, increases bronchodilation when added to an inhaled beta-adrenergic agonist during the initial treatment of an acute asthma attack. Adults asthmatics (n = 40) with acute asthma attacks were randomized to receive metaproterenol (5 percent solution, 0.3 ml) either alone or with atropine sulfate (2.5 mg), by nebulization. Spirometry, vital signs, and the presence of side effects 0, 30, 60, and 120 minutes after treatment were determined. There were no significant differences between the metaproterenol alone and metaproterenol plus atropine sulfate groups in regard to age, duration of asthma, baseline spirometry, or side effects. No differences were noted between the two groups regarding changes in FEV1 and FVC from baseline (expressed in milliliters or as a percentage of baseline) during the observation period. We conclude that nebulized atropine sulfate yields no additional benefit when added to metaproterenol during the initial treatment of an acute asthma attack.