Theophylline and terbutaline, alone and in combination, were evaluated for effectiveness in treating exercise-induced bronchospasm (EIB) when used at doses that should be tolerated by adolescents taking them intermittently: theophylline, 250 mg (fast release) and terbutaline, 2.5 mg. Twenty-one subjects, 12 to 19 years of age, with EIB performed standardized exercise tests on four separate days and received either theophylline, terbutaline, the combination, or placebo in a prerandomized double-blind manner prior to exercise. Exercise tests were performed two and five hours after each study drug administration. Blood samples were drawn before and again two and five hours after drug administration for theophylline level. Pulmonary function [forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and forced expiratory flow rate (FEF 25% to 75%)] was recorded before and after exercise. All of the active treatments were better than placebo in diminishing EIB. The combination was statistically better than terbutaline or theophylline alone. The effect of theophylline was not significantly different from that of terbutaline. The combination induced significantly more tremor than either agent individually. Either drug alone or the two in combination is effective for diminishing EIB. Although the combination may have additive properties for some patients, the increased incidence of tremor may diminish its appeal. Either drug alone or in combination is effective in decreasing EIB for at least five hours, which makes them practical choices for treatment of school-aged children.