Current guidelines on asthma management recommend the early use of inhaled corticosteroids. Recent studies of patients with moderate to severe asthma show that the addition of salmeterol is superior to a further increase of the steroids. In this study with adult, mild persistent asthma patients, we compared the effects of adding salmeterol 50 microg b.i.d. versus beclomethasone dipropionate (BDP) 200 microg b.i.d. (both via Diskhaler dry powder inhaler) to the low-dose inhaled steroids. A double-blind, randomized, parallel-group study was conducted with a run-in period of 2 weeks and a treatment period of 12 weeks. Patients (n = 233) were randomized with a peak expiratory flow (PEF) reversibility of 22 +/- 10% (mean +/- SD) in the run-in period. The morning PEF was 84 +/- 17% predicted and the age was 42 +/- 14 years (45% males). The average prestudy inhaled steroid dose was 361 microg daily. Within a week of salmeterol treatment the daily PEF recordings reached maximal levels. At the end of the treatment period the evening PEF remained significantly better in the salmeterol group than in the BDP group (p = 0.036). The PEFs, measured at the general practitioners' (GPs') office, were at least 95% of the predicted values and the post-salbutamol values at the end of both treatments. However, the salmeterol group had already obtained this level after 2 weeks and differed significantly from the beclomethasone group (p = 0.003 for percent predicted and p = 0.0007 for post-salbutamol PEF values). The symptom scores and the use of rescue medication showed a similar profile. Quality of life improved with both treatments, but without significant statistical differences between the groups. The frequency of adverse events, typical for beta2-agonists, was low and showed no differences between the groups. These results showed that the addition of salmeterol is at least as effective as adding beclomethasone in normalizing peak flows and improving asthma control in mild persistent asthma patients. Furthermore, salmeterol has a much faster onset of action.