The purpose of this study were: (1) to establish the prevalence of exercise-induced hematuria in a group of otherwise healthy male runners (n = 70), and (2) to investigate the role of exercise intensity in those runners who exhibited exercise-related hematuria (n = 10) by evaluating the effect of running and cycling at high and low intensities. The identified and recruited subjects participated in four different exercise protocols: (1) a 60-min treadmill run (RUN) at 90% of anaerobic threshold (Th(ae)), (2) a 60-min leg cycle ergometer ride (BIKE) at 90% of Th(ae), (3) a 3x400-m sprint (SPRINT), each followed by 4 min of rest or light walking, and (4) 3x60-Wingate leg cycle ergometry tests, each followed by 4 min of rest or light cycling. The study employed a 3x4 (time by protocol) within-subjects design and dependent variables were measured before exercise, 4 min after, and 1 h after exercise, and included measurements of hematuria, proteinuria, urinary pH, serum haptoglobin concentration, serum creatine phosphokinase activity, plasma lactate concentration, and hemoglobin. The 400-m sprint at maximal effort significantly increased both hematuria and proteinuria (P<0.01). Post-exercise hematuria for the SPRINT protocol was significantly different than that for the BIKE (P<0.01) and RUN (P<0.01) protocols. Due to the significant increase in hematuria and proteinuria following the SPRINT protocol, it was concluded that exercise-related changes in renal function were associated with weight-bearing exercise intensity rather than non-weight-bearing exercise duration.