A review of the literature highlights the need for research, particularly on the acute bronchodilatory effect of salmeterol on bronchoconstriction in the pediatric age group. The present study attempted to evaluate the acute bronchodilatory effect of salmeterol on methacholine-induced bronchoconstriction in childhood asthma and to compare it with the effect of salbutamol. Forty-four asymptomatic children with mild-to-moderate asthma (23 boys and 21 girls: aged 7-17 years) were studied. At the beginning, the baseline forced expiratory volume in 1 s (FEV1) was measured, and the methacholine challenge was performed by doubling the dose to determine PC20 (provocative concentration of inhaled methacholine required to reduce FEV1 by 20%). At the same time, the transcutaneous arterial oxygen saturation (SaO2) was also measured. Each subject inhaled a single dose of 25 mu g salmeterol (n: 23, group I) or 100 mu g salbutamol (n: 21, group II) following the SaO2 measurement. The same measurements (FEV1, SaO2) were repeated 5 and 20 min after the inhalation. After inhalation of salmeterol or salbutamol, the differences between the values of FEV1 and SaO2 after 5 and 20 min were insignificant in both group I and group II (P>0.05), although there was a significant improvement in both FEV1 and SaO2 after 5 and 20 min (P<0.005). From these findings it was concluded that salmeterol can be considered as effective as salbutamol on methacholine-induced bronchoconstriction.