A double-blind cross-over study lasting 16 weeks was conducted to establish if a twice daily regimen of beclomethasone dipropionate (BDP) was as effective in controlling asthma as a four times daily regimen. The patient's need for inhaled steroids (100 mcg BDP qds) was confirmed prior to entering the study by deterioration of peak expiratory flow rates and/or increased bronchodilator usage during a single-blind placebo period of 6 weeks. Thirty six asthmatics were eligible to enter the study and completed both treatment periods. Daily record cards of symptom scores, four times daily peak expiratory flow rate measurements and inhaled bronchodilator usage were recorded throughout the study. There was no significant difference between the mean PEFR measurements taken four times each day and the variability in PEFR, between the two treatment groups. Symptom scores for cough, wheeze, breathlessness and overall disability also showed no significant difference. Symptomatic inhaler usage for the two groups was similar. Lung function measurements of FEV1, FVC and VC were almost identical; FEV1 being 2.1 l on twice daily regimen and 2.2 l on four times daily regimen. A slight variation was observed in PEFR taken at the end of each treatment period at the clinic visits, being 361 l/min on twice daily and 380 l/min on four times daily drug dosage. In stable asthmatics, the control of asthma measured both symptomatically and by daily lung function was independent of dosing schedule, but twice daily treatment may well lead to better compliance.