Salmeterol inhaled twice-daily is now being used more frequently as additional treatment in asthma insufficiently controlled by inhaled corticosteroids. We compared oral bambuterol in a dose of 20 mg taken once daily in the evening with inhaled salmeterol at 50 microgram taken twice daily in 126 asthmatic patients (60 bambuterol, 66 salmeterol) aged 18 to 74 yr who were treated for at least 4 wk with inhaled corticosteroids at a constant dose of 400 to 2,000 microgram/d or with oral corticosteroids at </= 20 mg/d. The patients were able to use a pressurized metered dose inhaler (pMDI) efficiently, and had an FEV1 of 40 to 85% of the predicted normal value. During a run-in period, patients had to show at least one nocturnal or early awakening caused by asthma symptoms that required rescue medication, and a >/= 15% overnight decrease in peak expiratory flow (PEF) on 3 of the preceding 7 d, in order to be randomized into this double-blind, double dummy, multicenter parallel group study (2-wk run-in period and 6 wk of treatment). There was no significant difference between bambuterol and salmeterol in morning change from baseline in PEF (p = 0.53). The median increases in morning PEF were 50 L/min for bambuterol and 55 L/min for salmeterol. Other variables (evening PEF, percent of overnight decrease in PEF, number of awakenings, percent of nights with an awakening, number of puffs of rescue medication, asthma symptoms during the day and night, and mean tremor score) also showed no significant difference between bambuterol and salmeterol. Both treatments, at the doses given, were well tolerated. Once-daily oral bambuterol is a convenient, effective, and less expensive alternative to twice-daily inhaled salmeterol for treating nocturnal asthma.