The purpose of this study is to evaluate the effect of disodium cromoglycate (DSCG) on gas exchange and ventilation during incremental exercise in asthmatic children with an FEV1fall less than 15 percent from the baseline after the exercise. Seventeen children (aged 8 to 14 years) with a history of mild to moderate asthma but no clinical and spirometric evidence of exercise-induced asthma (EIA) underwent two maximal exercise tests in a randomized order: test A without premedication and test B after inhalation of DSCG, 40 mg. To evaluate the effect of DSCG on normal airways, nine healthy children performed the same exercise protocol. Pulmonary function was normal at rest and after treadmill exercise test (the mean postexercise fall in FEV1was 5.9 percent in test A and 1.5 percent in test B). Gas exchange, minute ventilation ( V˙e) and heart rate (HR) were monitored during running in both tests. In the asthmatic subjects, there were no differences in oxygen uptake ( V˙o2), carbon dioxide output ( V˙co2), and V˙eat rest between the two tests. During exercise, V˙e, V˙o2, V˙co2, and energy cost (EC [O2ml · kg−1· m−1]) of running in the asthmatic subjects were significantly lower in test B than in test A (analysis of variance, p<0.01) for comparable work rates. Maximal minute ventilation (VEmax) was significantly higher in test A (46.9±14.6[±SD] L · min−1) than in test B (43.2±14 L · min−1; p<0.05). We found no significant effect of DSCG on gas exchange and ventilation during exercise in the healthy children ( V˙emax 47.8±25 and 48.4±25 L · min−1in test A and B, respectively). In conclusion, premedication with DSCG appears to decrease the ventilatory cost of exercise in asthmatic children who do not present a substantial fall in FEV1after an exercise test without pretreatment.