It is well known that athletes in the United States are told to abstain from sexual intercourse prior to athletic competition. The rationale for such a policy appears to be related to the hypothesis that sexual intercourse decreases the athletes' ability to perform efficiently and/or maximally. But the effect that sexual intercourse may have on exercise performance has not been examined widely. Very likely, the restrictions placed on athletes have little to do with the athletes' physiological ability to substain a particular exercise intensity and/or perform maximally. The purpose of this study was to determine the effects of sexual intercourse 12 hours prior to maximal treadmill exercise on aerobic power, oxygen pulse, and double product (i.e., an index of relative cardiac work). Eleven male subjects were tested on the treadmill with and without prior sexual intercourse. The results from the maximal exercise tests showed that aerobic power, oxygen pulse, and double product were not different. Therefore, the data suggest that it is justified to dismiss the point of view that sexual intercourse decreases maximal exercise performance.