Since bronchiolitis has clinical and pathophysiologic similarities to asthma, the use of bronchodilator drugs has been suggested; however, their effectiveness remains unproven. We reviewed the outcome of treatment in 64 children less than 18 months of age hospitalized for the first time with a diagnosis of bronchiolitis or wheezing. Thirty one of the patients received theophylline therapy and sometimes steroids and/or inhaled sympathomimetic drugs, and 34 received no such therapy. Although the theophylline-treated children were older (9.4 vs 4.9 months of age), there were no other differences in the histories, clinical findings, laboratory assessments, or outcome between theophylline-treated and untreated groups. The results suggest that theophylline and steroid therapies had not beneficial effects on the resolution of acute bronchiolitis or wheezing in the majority of infants and small children.