Theophylline, a pharmacologic agent presently permitted during international sporting competition, has come under scrutiny because of the suggestion that it may be ergogenic. This study examined the effects of serum theophylline levels of 10 to 20 mg/L and the administration of a placebo on selected measures of physical performance and work capacity to determine any ergogenic outcomes. Seven male and three female elite athletes from a variety of team sports and aged 18 to 30 years participated in the study. The variables measured were height, mass, maximal oxygen consumption, muscular endurance, muscular power, muscular strength, FVC, FEV1, and reaction time. When the scores obtained after ingestion of theophylline and a placebo with a double-blind, crossover technique were compared, no significant difference was found for any of these variables. A two-way analysis of variance of FEV1 scores obtained before and after maximal exercise revealed no significant "F" ratios. This indicated that none of these trained athletes demonstrated exercise-induced asthma and that there was no difference in airway resistance after maximal exercise while they were under the influence of theophylline or placebo. We conclude that no ergogenic effects were attributable to theophylline therapy which should therefore remain an acceptable means of management of athletes with asthma participating in international sporting events.