This 12-week, double-blind, placebo-controlled, multicenter study evaluated the efficacy and safety of budesonide 400 microg administered once daily via Turbuhaler in adults previously treated with at least twice-daily dosing of inhaled corticosteroids. Pulmonary function (FEV1, PEF, FVC, FEF(25-75%)), asthma symptom scores, quality of life, and breakthrough medication use were significantly (p < 0.05) different in patients receiving once-daily budesonide Turbuhaler compared to placebo, and significantly (p < 0.001) more patients receiving placebo discontinued the study. Adverse events were similar between study groups. Once-daily administration of budesonide Turbuhaler was safe and efficacious in patients previously treated with inhaled corticosteroids.