Background: The inhaled corticosteroid, fluticasone propionate, was compared with the oral bronchodilator theophylline in the maintenance treatment of asthma. Objective: The objective of the present study was to compare the efficacy and safety of twice-daily inhaled fluticasone propionate, 50 mu g, and fluticasone propionate, 100 mu g, with that of theophylline in the maintenance treatment of mild-to-moderate asthma. Methods: In this randomized, double-blind, placebo-controlled, parallel-group study, 353 adult and adolescent patients with asthma inadequately controlled with inhaled beta-agonist therapy alone received fluticasone propionate, 50 mu g, or fluticasone propionate, 100 mu g, by metered-dose inhaler; theophylline capsules; or placebo twice daily for 12 weeks. Only inhaled albuterol was permitted as needed for acute symptoms. Results: Both fluticasone propionate groups had a significantly greater probability of remaining in the study (ie, meeting asthma stability criteria) than did either the theophylline or placebo group (P less than or equal to .008); 39% and 51% in the theophylline and placebo groups, respectively, were withdrawn due to lack of treatment efficacy compared with 14% and 21% in the fluticasone propionate, 50 mu g, and fluticasone propionate, 100 mu g, groups. Both fluticasone propionate groups experienced significantly greater improvement in FEV(1) and PEF compared with patients in the theophylline or placebo group (P less than or equal to .004), The incidence of potentially drug-related adverse events was significantly greater in the theophylline group (25%) than in the placebo group (11%) (P = .031), while there were no differences between placebo and fluticasone propionate, 50 mu g, (18%) or fluticasone propionate 100 mu g, (22%). Conclusion: Twice daily treatment with inhaled fluticasone propionate 50 mu g or 100 mu g was significantly more effective than theophylline in the treatment of mild-to-moderate asthma.