This 12-month dose-titration study assessed the effectiveness of budesonide/formoterol for maintenance plus relief with a control group using salmeterol/fluticasone for maintenance plus salbutamol for relief. Adolescents and adults (n = 2,143; mean forced expiratory volume in one second (FEV1) 73% predicted; mean inhaled corticosteroid (ICS) 884 microg.day(-1)) were randomised to budesonide/formoterol 160/4.5 microg two inhalations b.i.d. plus additional inhalations as needed, or salmeterol/fluticasone 50/250 microg b.i.d. plus salbutamol as needed. Treatment was prescribed open label; after 4 weeks, physicians could titrate maintenance doses in accordance with normal clinical practice. Maintenance plus as-needed budesonide/formoterol prolonged the time to first severe exacerbation versus salmeterol/fluticasone (25% risk reduction). The total number of severe exacerbations was significantly reduced in the budesonide/formoterol group (255 versus 329). Both regimens provided sustained improvements in symptoms, as-needed use, quality of life and FEV1, with differences in favour of the budesonide/formoterol group for as-needed use (0.58 versus 0.93 inhalations.day(-1)) and FEV1 (post-beta2-agonist values). Mean ICS dose during treatment was similar in both groups (653 microg budesonide.day(-1) (maintenance plus as-needed) versus 583 microg fluticasone.day(-1)). The simplified strategy using budesonide/formoterol for maintenance and reliever therapy is feasible, safe and at least as effective as salmeterol/fluticasone plus salbutamol.