It has been well established that self-limited, benign changes frequently occur in the urine following exercise. This study was undertaken to evaluate potential changes in the urine of amateur boxers. Demographic data, a boxing history, a complete medical history, and a physical examination were obtained for each subject. Prefight and postfight urine specimens were examined for comparison. The data were subjected to statistical analysis in order to evaluate the significance of mean changes by using an independent one-way analysis of variance. The authors used the least significant difference test designed by Fisher. Results of this study revealed no clinically significant effect on urine variables other than changes normally associated with comparable strenuous exercise of other types. However, the long-term effect of boxing on renal function was not explored. Therefore, the authors recommend that all boxers undergo a urine evaluation as a routine part of their ongoing physical examinations.