1. Although the clinical effects of the tulobuterol patch have been reported to include an increase in morning peak expiratory flow (PEF) values and a decrease of symptoms and the frequency of the rescue use of inhaled short-acting beta2-adrenoceptor agonists, no trials comparing the efficacy of the tulobuterol patch to other standard inhaled long-acting beta2-adrenoceptor agonists have yet been conducted. The aim of the present study was to compare the clinical effects of the patch formulation of tulobuterol with those of inhaled salmeterol in moderate to severe asthma. 2. Fifty-four patients with moderate to severe asthma, whose conditions were suboptimally controlled despite receiving inhaled corticosteroids, were recruited. The study was a prospective, randomized trial of cross-over design comparing the effects of 4 weeks treatment with tulobuterol patch, 2 mg once daily, and salmeterol, 50 mg twice daily. The mean prebronchodilator morning PEF during the last 14 days of each treatment period and health-related quality of life (HRQoL) were the primary outcome variables. The HRQoL was assessed using the St George's Respiratory Questionnaire. 3. Forty-four patients (81.5%) completed the trial and were included in the analysis. The mean morning PEF and HRQoL score were significantly improved in both the salmeterol (P < 0.0001 and P < 0.05, respectively) and the tulobuterol patch (P < 0.01 and P < 0.05, respectively) treatment periods compared with the run-in period. Although the mean morning PEF was significantly higher in the salmeterol-treated group than in the tulobuterol-treated group (P < 0.001), the HRQoL scores were comparable. 4. The tulobuterol patch may be useful as a controller medication in addition to inhaled corticosteroids in moderate to severe asthma.