The present paper evaluated racial differences in biological variability (BV) during submaximal and maximal treadmill exercise and recovery. Using sample size estimation, five college-age black (B) and white (W) males were matched for body mass, stature, fat-free mass (densitometry), and physical activity level (questionnaire). Each subject performed 10 treadmill tests within a 6-wk period. Tests 1 and 10 assessed VO2max. The remaining tests included 10 min rest, 2 min walking at 5% grade, 3.5mph (24% VO2max), 6 min running at each of two different intensities 6mph (5% grade, 6mph, 66.6% VO2max; 10% grade, 6mph, 89.4% VO2max). Tests 2 to 9 included 20 min seated recovery. Criterion measurements included VO2, VE, RER, heart rate, and systolic and diastolic blood pressure. BV was calculated from the 8 repeated tests as the standard deviation for each criterion variable for each min during rest, exercise, and recovery (subtracting technological variation due to instrument error in the metabolic analyzers and heart rate and blood pressure monitors). Intraclass reliability averaged r=0.401 to 0.999 for all criterion variables throughout exercise and recovery. No training effect occurred in VO2max before and after the 8 submaximal and maximal tests. Repeated measures ANOVA revealed no significant differences in BV between B and W subjects (p>0.05). BV accounted for 4 to 9% of the total variability of the critetrion physiological measures.The results demonstrate no racial differences in BV during submaximal and maximal exercise (including recovery) for VO2, VE, RER, heart rate, and systolic and diastolic blood pressure.