BACKGROUND A powder formulation of salmeterol has been shown to prevent exercise-induced bronchospasm (EIB) in asthmatic children and adults; however, the delivery device (Diskhaler; Glaxo Wellcome Inc, Research Triangle Park, NC) must be reloaded after 4 doses. A new multidose powder inhaler (Diskus) provides 60 doses of salmeterol in a blister pack presentation with a dose counter. OBJECTIVE To evaluate the safety and efficacy of 50-microg salmeterol powder via two different delivery systems (Diskhaler and Diskus) in preventing EIB in asthmatic children. METHODS A randomized, double-blind, double-dummy, single-dose, placebo-controlled, three-way crossover study was conducted in 24 children 4 to 11 years of age demonstrating EIB and mild to moderate asthma. Serial forced expiratory volume in 1 second (FEV(1)) was measured before and after treadmill exercise challenges conducted at 1, 6, and 12 hours after study drug administration. Adverse events were also assessed. RESULTS During all exercise challenges, EIB-mediated reductions in FEV(1) were minimized or prevented in patients receiving single doses of salmeterol powder compared with placebo. Single doses of salmeterol powder delivered via either system were equally effective in preventing EIB. There were no drug-related adverse events, cardiovascular, or other clinically relevant safety concerns. CONCLUSIONS Single doses of salmeterol powder delivered by either delivery system are safe and effective in preventing EIB for >/=12 hours in asthmatic children.