Symptom- limited, graded exercise treadmill testing was performed by 4, 968 white and black adults, ages 18-30 yr, during the baseline examination for the CARDIA study. The mean estimated maximal exercise capacity by race/gender, expressed as metabolic units (METS), was: white men 13.8, black men 13.0, white women 11.1, and black women 9.4. Exercise test duration was higher in nonsmokers, positively related to physical activity score and pulmonary function (FEVl-hr2), and inversely related to body mass index. Men had higher mean values than women for both test duration and a measure of submaximal performance, the workload 130 (WL130, the exercise test duration to a heart rate of 130 beats min-1). Adjusted for age and education, white men had a longer mean test duration than black men (53 s longer, P<0.001), but nearly equal mean WL130. White women had higher mean values than black women for both test duration (114 s longer, P<0.001) and WL130 (36 s longer, P < 0.001). Men had higher mean values than women for both outcome measures (P<0.001). Thus, in young adults significant gender and ethnic differences exist for exercise test performance, part of which can be explained by personal habits or traits. © 1992 The American College of Sports Medicine.