Salmeterol is a long acting, highly selective, beta2-adrenergic agonist. It prevents asthma symptoms in patients with mild or moderate disease and improves nocturnal asthma and sleep quality. We evaluated the bronchodilator and bronchoprotective effect and duration of action of inhaled salmeterol in patients wlth asthma. We compared the bronchodilator and bronchoprotective effects of salmeterol with salbutamol in 34 patients with asthma. Diagnosis of asthma was confirmed with methacholine challenge test or airway reversibility test. We performed the symptom index questionnaire, peak expiratory flow rate, pulmonary function test and methacholine challenge test. Symptom scores were more improved with salmeterol treatment than salbutamol treatment. After salmeterol inhalation, mean FEV1 increased from 1.95L(pre-treatment) to 2.04L(early stage in the treatment), 2.06L(late stage), 2.03L(follow up). There was no difference in FEV1 between early stage and late stage after salmeterol treatment. With salmeterol, there was a significant increases in PC30 on methacholine challenge test ( PC20 4.96 : 16.42). Salmeterol is a potent, long-acting bronchodilator, with a slower onset and longer duration of bronchodilation than salbutamol. It also has bronchoprotective effect and shows low incidence of adverse effects.