The aim of the study was to compare the efficacy, tolerability and patient acceptability of bambuterol (Bambec) against controlled release (CR) salbutamol (Volmax) in the treatment of nocturnal asthma. One hundred and fifty two asthmatic patients aged 17-78 years, using > or = 800 micrograms/day of an inhaled steroid, with nocturnal asthma symptoms, openly received three weeks of bambuterol 20 mg nocte and three weeks of salbutamol CR 8 mg b.i.d. in a randomised, cross over sequence. Both bambuterol and salbutamol CR treatment produced a significant 63% decrease in the severity of baseline nocturnal asthma symptoms. This improved control of nocturnal asthma was reflected by significant improvements in baseline lung function. Both the severity and number of days of tremor during the first week of treatment was significantly lower with bambuterol than with salbutamol CR. Patients considered bambuterol to cause less shakiness and treatment preference was bambuterol 49%, salbutamol CR 36%, no preference 15%. The predominant reason for patient treatment preference was control of asthma symptoms, however a significant sub-group of patients (27%) chose bambuterol because of fewer adverse effects compared to 11% choosing salbutamol CR. Fifty six percent of patients preferred taking their medication once-daily and 7% preferred twice-daily. This study shows that both bambuterol and salbutamol CR are equally effective treatments for nocturnal asthma in patients already receiving inhaled steroid. The most important factor in terms of patient treatment acceptability appears to be control of symptoms. Sub-groups of patients may chose bambuterol due to its better adverse effect profile and once-daily regimen.