It has been demonstrated that inhaled furosemide inhibits indirect but not direct bronchoconstricting stimuli. The exercise test (ET; indirect) has been shown to be inhibited in adults. Our aim was to determine whether the ET was also inhibited in children by low doses of furosemide. We studied 10 asthmatic patients with a mean age of 11.1 years whose ET results were positive, and in whom the ET was repeated after inhaling 28 mg of furosemide. After 10 min, there were no significant signs of bronchodilatation. The percent decrease in mean FVC, FEV1, MF50 and peak flow (PF) was significantly lower with the premedication. The protection achieved was: FVC, 66.5%; FEV1, 51.4%; MF50, 30.3%; and PF, 63.9%. No clinical response was observed in 5 of 10 cases. It was concluded that 28 mg of inhaled furosemide inhibits the ET in asthmatic children.