the purpose of this study was to answer the question, “do middle distance track athletes experience hematuria with their normal competitive season interval workouts?” secondary purposes were (1) to identify the type of workout most associated with hematuria as workouts were classified on the basis of intensity and duration and (2) compile supplementary measures associated with these workouts that would hopefully help to point towards a cause. the participants for this study were a group of seven male and three female (n=10), healthy, experienced middle distance runners aged 19-56 years who were all members of the 阿根廷vs墨西哥竞猜 athletics club in thunder bay, ontario. over the course of four weeks, subjects underwent urinalysis before and immediately following, their twice weekly interval sessions, over the course of a four week period. pre-workout urine samples were examined for ph, specific gravity, and the presence of hematuria, proteinuria, and granular casts using reagent strip analysis. positive hematuria samples precluded follow up analysis on that subject. post workout urine samples underwent reagent strip analysis for ph, specific gravity, hematuria, and proteinuria. positive specimens for hematuria were analysed under a microscope to calculate a more accurate red blood cell (rbc) and granular cast loss. subjects were asked to provide follow-up samples until the reagent strip indicated a negative result for hematuria. supplementary measures of 4min. peak blood lactate (pbla), a subjective rating of perceived exertion (rpe), and the amount of time the subject worked above 65% of their vo2max (65% vo2max) were used to indicate if a specific level of exertion was required to induce hematuria in middle distance track runners. urine sampling indicated that middle distance track runners do experience hematuria, with nine of the ten subjects providing a positive sample at least once during the four week period. this study was unable to prove which of the thirteen workout classifications had the greatest incidence of hematuria because o f the unequal number of subjects completing each workout classification the results did demonutate that the greatest incidence of hematuria occurred following workouts of 800 m and 1500 m running pace with durations of 1001- 4000 m. the individual mean loss of red blood cells (rbc) per high power microscopic field (hpf) for the study group ranged between 2-81 rbc. all positive samples contained microcytic whole rbc. protein and granular casts were observed regardless of the presence of rbc. a clear relationship between rbc loss and the supplementary measures of exertion was not observed.