The objective of the present study was to evaluate the effectiveness and tolerance of a new beta-2 agonist, tulobuterol, in children. Fifteen patients with acute asthma were studied, during a period of 21 days. Significant increase in forced vital capacity (FVC), forced expiratory volume in the first second (FEV-1), and forced expiratory flow 25-75% (FEF 25-75%) were observed after treatment with tulobuterol (p less than 0.01). Clinical improvement was evident as measured by a clinical-scale and a functional scale. The only side effect attributable to the drug was a tremor which was observed in three patients.