Whether cardiorespiratory fitness relates to early subclinical atherosclerotic vascular disease remains unknown. We investigated the relation of cardiorespiratory fitness to coronary artery calcification (CAC) in 2373 African-American and White young adults from the Coronary Artery Risk Development in Young Adults (CARDIA) Study. We measured cardiorespiratory fitness in 1985-1986 (baseline) using a symptom-limited exercise test on a treadmill. Coronary calcium scores were measured in 2001-2002 (year 15) using electron-beam or multi-detector computed tomography. CAC was classified as present or absent, while cardiorespiratory fitness was classified as sex-specific low, moderate, and high fitness categories. After adjustment for age, sex, race, clinical center, education, cigarette smoking, waist girth, alcohol intake, physical activity, systolic blood pressure, antihypertensive medication use, diabetes mellitus, and fasting insulin, baseline cardiorespiratory fitness was inversely associated with prevalence of CAC in young adults (P for trend=0.03). The odds ratios of having CAC for persons in the moderately and highly fit individuals were 0.80 (95% confidence interval (CI), 0.55-1.15) and 0.59 (95% CI, 0.36-0.97), respectively, as compared with the low-fit individuals. High levels of cardiorespiratory fitness were associated with a lower risk of having coronary calcification 15 years later in African-American and White young adults.