Guidelines on asthma management recommend that in patients who still have symptoms on treatment with low-dose inhaled corticosteroids the first step should be an increase in inhaled corticosteroid dose. The addition of long-acting inhaled beta 2-adrenoceptor agonists is another option. We have compared these two strategies in a randomised, double-blind, parallel-group trial. We studied 429 adult asthmatic patients who still had symptoms despite maintenance treatment with 200 micrograms twice daily inhaled beclomethasone dipropionate (BDP). 3 did not provide verifiable data. Of the others, 220 were assigned salmeterol xinafoate (50 micrograms twice daily) plus BDP and 206 were assigned higher-dose BDP (500 micrograms twice daily) for 6 months. The mean morning peak expiratory flow increased from baseline in both groups, but the increase was greater in the salmeterol/BDP group than in the higher-dose BDP group at all time points (differences 16-21 L/min, p < 0.05). Mean evening PEF also increased with salmeterol/BDP but not with higher-dose BDP. There were significant differences in favour of salmeterol/BDP in diurnal variation of PEF (all time points) and in use of rescue bronchodilator (salbutamol) and daytime and night-time symptoms (some time points). There was no significant difference between the groups in adverse effects or exacerbations of asthma, indicating that in this group of patients regular beta 2-agonist therapy was not associated with any risk of deteriorating asthma control over 6 months. This study suggests a need for a flexible approach to asthma management.