Budesonide inhalation powder via the dry-powder multidose inhaler Turbuhaler (budesonide Turbuhaler) has been shown to improve lung function and symptoms in adults with asthma. In this double-blind, placebo-controlled, multicenter trial, we evaluated the effects of once-daily budesonide Turbuhaler on health-related quality of life (HRQL) in 177 adults (aged 18-70 years) with non-steroid-dependent asthma. Patients were randomized to receive budesonide Turbuhaler (400 micrograms) once daily or placebo for 12 weeks. HRQL was assessed at baseline and weeks 4 and 12 using the Asthma Quality of Life Questionnaire (AQLQ). In addition to assessment based on the four AQLQ domains (activity limitations, asthma symptoms, emotional function, and response to exposure to environmental stimuli), AQLQ overall scores were analyzed for both treatment groups. Compared with placebo, patients using budesonide Turbuhaler once daily had statistically significant (p < 0.001) improvements from baseline to weeks 4 and 12 in AQLQ overall scores. Statistically significant improvements from baseline to weeks 4 and 12 in all four individual domains also were observed in the budesonide Turbuhaler group compared with placebo. Differences between the two treatment groups in mean changes from baseline in AQLQ overall, asthma symptoms, and emotional function reached the level required for patients to achieve a minimal important difference of change (> or = 0.5 U) at week 12. A retrospective analysis of the data showed that approximately 70% of patients treated with budesonide Turbuhaler experienced a minimal important difference of change in AQLQ overall scores. Overall, improvements in AQLQ correlated significantly (p < or = 0.04) with improvements in forced expiratory volume in 1 second, morning peak expiratory flow measurements, asthma symptoms, and breakthrough bronchodilator use at the study end. Thus, patients with corticosteroid-naïve asthma can experience improved HRQL when using budesonide Turbuhaler.