Fifteen patients with chronic asthma completed a double-blind cross-over trial during which they were treated with the same daily doses of salbutamol and beclomethasone dipropionate (BDP) from either a combination inhaler or two separate inhalers. Lung function was measured at the end of each treatment period and each patient kept a diary card throughout. Daily assessments of patients' symptoms and additional medication requirements were similar during both treatment periods. Peak expiratory flow rate (PEFR) recordings taken four times a day showed little diurnal variation during both periods. Mean PEFRs for the groups during a period of 2 weeks were similar for both treatments at all times. Overall daily mean PEFRs showed a trend in favour of the combination inhaler. There was a suggestion of greater variability in airway obstruction during the period when the separate inhalers were used, as assessed by the number of occasions that the PEFR was outside the range (overall daily mean +/- 15%). Lung function measurements at the end of each period showed a trend in favour of the combination inhaler which was clinically significant in terms of the forced expiratory volume in the 1st second and forced vital capacity. The combination inhaler provides an alternative in the management of asthma which is at least as effective as treatment with salbutamol and BDP from two separate inhalers.