B2-agonists are considered one of the cornerstones of the asthma therapy, but their short action requires frequent administration and an association with other broncodilators. The development of long-acting beta2-agonists may represent an important improvement in asthma treatment. PURPOSE: The present study was designed to assess the efficacy and safety of inhaled salmeterol compared to salbutamol in patients with mild-to-moderate asthma. METHODS: After the two run-in weeks, the patients received either salmeterol 50mg twice a day or salbutamol 200 mg four times a day, over a four week period, following a double blind, parallel group study. Sixty patients had the following inclusion criteria: FEV1 > 50% or PEFR over the past seven days >50% of predicted normal; reversibility of FEV1 >15%; symptoms scores >2 (score 0 and 5) in 4 of the last seven days or PEFR variation >15% . RESULTS: Seven patients discontinued the protocol (see methods). Of the 53 analyzable patients, 25 were of the salmeterol group and 28 of the salbutamol group. Our results showed that in the run-in period there were not differences among the groups comparing the values of FEV1 in % predicted, morning PEFR and asthma symptoms scores. The improvement rate of morning FEV1 and PEFR in patients who received salmeterol was significantly higher (p<0.05) compared to the patients who received salbutamol, for two and four weeks of treatment. Also, the salmeterol group have shown reduction of the symptoms in the nocturnal period(significantly in the first fortnight of treatment) demonstrated by the significative increase in the symptoms improvement rate when compared salmeterol and to salbutamol groups. The number of rescue medication inhaled, side effects, heart rate, blood pressure, serum potassium dosage and electrocardiograms, did no show significative differences between the groups. CONCLUSION:This study showed that in mild to moderate asthmatic patients, salmeterol in the dosage of 100mg/day raised the FEV1 and the morning PEF and led to pronounced decrease in the nocturnal symptoms as compared to salbutamol. The side effects were similar.