The aim of this multicenter, double-masked study was to compare the efficacy and safety of two different doses of inhaled fluticasone propionate dry powder--50 micrograms and 100 micrograms--administered BID via a multidose powder inhaler with those of placebo in the treatment of children with persistent asthma. After a 2-week run-in period, 263 patients were randomized to treatment with twice-daily placebo (n = 92), fluticasone 50 micrograms (n = 85), or fluticasone 100 micrograms (n = 86) for 12 weeks. One hundred sixty-six (63%) patients were male, and 224 (85%) were white, with a mean age of 8 years. Two hundred twenty-one (84%) patients were atopic, and 167 (63%) had been asthmatic for 1 to 5 years. Baseline mean morning peak expiratory flow (PEF) values were 207 L/min, 199 L/min, and 194 L/min, and baseline percentages of predicted normal values were 86%, 80%, and 81% for the groups receiving placebo, fluticasone 50 micrograms, and fluticasone 100 micrograms, respectively. At the end of the first week of treatment, patients in both fluticasone groups had significantly greater improvements in morning PEF than did those receiving placebo. Patients experienced mean increases of 4 L/min, 22 L/min, and 26 L/min with placebo, fluticasone 50 micrograms, and fluticasone 100 micrograms, respectively. At the end point (the last evaluable visit), patients in both fluticasone groups continued to have significantly greater improvements in morning PEF than did patients receiving placebo. Patients experienced mean increases of 17 L/min, 50 L/min, and 57 L/min with placebo, fluticasone 50 micrograms, and fluticasone 100 micrograms, respectively. Changes in the percentage of predicted values by end point were 8%, 20%, and 26% with placebo, fluticasone 50 micrograms, and fluticasone 100 micrograms, respectively. The probability of remaining in the study, according to predefined withdrawal criteria, indicated a significant treatment difference in favor of fluticasone. Withdrawal criteria were met by 63%, 42%, and 29% of patients receiving placebo, fluticasone 50 micrograms, and fluticasone 100 micrograms, respectively. This study clearly demonstrates the superiority of fluticasone 50 and 100 micrograms BID over placebo in the treatment of persistent asthma in children.