Background: The use of budesonide/formoterol in a single inhaler for both maintenance and reliever therapy is a recommended option for treatment of persistent asthma not responding well to inhaled corticosteroid (ICS) alone. Methods: This was a multi-centre open-label study on patients whose asthma condition remained inadequately controlled by various asthma treatments other than budesonide/formoterol. After a 2-week run-in period, eligible patients underwent a 12-week treatment period with budesonide/formoterol (Symbicort SMART (R), 160/4.5 mu g) twice daily plus as needed. Patient's asthma control and quality of life were assessed using the 5-item Asthma Control Questionnaire (ACQ-5) and the standardized Asthma Quality of Life Questionnaire (AQLQ-S), respectively. Results: A total of 862 eligible asthma patients who have had asthma for a mean duration of 10.73 +/- 12.03 years entered a 12-week treatment with budesonide/formoterol maintenance and reliever therapy. During treatment, ACQ-5 score improved significantly by 0.58 +/- 0.93 (95% CI, 0.51 to 0.64, P < 0.0001) from the baseline level of 1.62 +/- 1.00. AQLQ (S) score improved by 0.70 +/- 0.89 (95% CI, 0.64 to 0.76, P < 0.0001) from baseline. Asthma symptom score was also reduced significantly (P < 0.0001); between run-in and treatment periods, night- and day-time symptom scores were reduced by 0.32 +/- 0.54 (95% CI, 0.28 to 0.35) and 0.30 +/- 0.52 (95% CI, 0.27 to 0.34), respectively. The percentage of nights with awakenings due to asthma symptoms was reduced by 11.09 +/- 26.13% (95% CI, 9.34 to 12.85%), while the percentage of asthma-control and symptom-free days increased by 20.90 +/- 34.40% (95% CI, 18.59 to 23.21%) and 23.89 +/- 34.62% (95% CI, 21.56 to 26.21%), respectively (P < 0.0001). Together with the improvement in asthma control, the number of night- and day-time inhalations of as-needed reliever medication decreased by 0.30 +/- 0.82 (95% CI, 0.24 to 0.35) inhalations and 0.30 +/- 0.97 (95% CI, 0.23 to 0.36) inhalations, respectively (P < 0.0001). No unexpected adverse events were reported. Conclusion: During treatment of inadequately controlled asthmatic patients with budesonide/formoterol maintenance and reliever therapy, significant improvement in patients' asthma control and reductions in asthma symptoms and as-needed medication use was observed. Patients' quality of life was improved and the treatment was well tolerated.