To assess the efficacy and safety of 2 different strengths of a manufactured albuterol solution for nebulization (AccuNeb(R); DEY, L.P., Napa, Calif), 349 children with moderate to severe asthma were enrolled in this prospective, multicenter, double-blind, placebo-controlled study. For 4 wk, children 6 to 12 y old were randomly assigned to 1.25 mg (A1) or 0.62 mg (A2) albuterol or placebo (P), nebulized 3 times daily for 4 weeks. Pulmonary function and safety were evaluated at weeks 0, 2, and 4 (visits 2-4). Nonparametric tests (Kruskal-Wallis and Wilcoxon's rank-sum) were used to compare treatments. Primary endpoint (week 4, %Delta area under the curve [AUC] forced expiratory volume in 1 sec [FEV(1)]) results for A1, A2, and P were 90.3% x h*, 73.6% x h*, and 34.2% x h. Secondary assessments for A1, A2, and P were as follows: (1) week 2, %DeltaAUC FEV1 (99.5%*h*, 104.5% x h*, and 43.6% x h); (2) maximum FEV1 (28.6%*, 26.3%*, and 13.4%); and (3) duration of effect (116.8 min*, 115.9 min*, and 39.2 min). A2 was more effective in children 10 y of age or younger and in children 11 to 12 y of age who weighed </=40 kg or had less severe asthma; A1 was more effective in children 11 to 12 y of age who weighed >40 kg or had more severe asthma. Adverse events (occurring in 47% of children) were considered unrelated to drug treatment. Observations on electrocardiogram (notably QTc interval) were similar to those for placebo. A1 and A2 appeared effective in improving pulmonary function and were well tolerated in children aged 6 to 12 y.