PURPOSE: To examine the relationship between cardiorespiratory fitness and body fatness during adolescence and cardiovascular disease (CVD) risk factors in adulthood. METHODS: The sample was 48 participants from the Aerobics Center Longitudinal Study (ACLS) who had one clinical visit during adolescence (mean age = 15.8 years) and a follow-up visit during adulthood (mean age = 26.6 years). Values for treadmill time (TM), body fatness (body mass index [BMI], percent body fat [%BF], and waist circumference [WC]), traditional CVD risk factors (blood pressure [BP], fasting total cholesterol [TC], high-density lipoprotein cholesterol [HDL-C], triglycerides [TG], and glucose), and a composite metabolic syndrome risk factor score were adjusted for age and sex. The relationships between adolescent TM and body fatness variables and adult CVD risk factors were examined by partial correlations, controlling for length of follow-up (mean = 11 years). The correlation between changes in TM and body fatness (DeltaTM and Deltabody fatness, respectively) and changes in CVD risk factors between adolescence and adulthood (DeltaCVD risk factors) were also examined. Adolescent cardiorespiratory fitness and body fatness variables also were separated into 2 categories based on the median split: low (below median) and high (above median). RESULTS: TM and body fatness variables showed moderate stability between adolescence and adulthood ( r = 0.44-0.78). Adolescent TM and DeltaTM showed moderate correlations with adult body fatness indicators (BMI, WC, and %BF, r = -0.34 to -0.47) and Deltabody fatness ( r = -0.24 to -0.46), respectively. Adolescent TM was not significantly related to traditional CVD risk factors in adulthood. Adolescent WC was significantly related to adult BP ( r = 0.33 to 0.45), and body fatness variables during adolescence were significantly related to adult TM ( r = -0.32 to -0.44). The DeltaWC was significantly related to DeltaTM ( r = -0.46) and DeltaHDL-C ( r = -0.51), and DeltaBMI was significantly related to DeltaBP ( r = 0.45) and DeltaHDL-C ( r = -0.34). Subjects with a high TM during adolescence showed lower levels of body fatness as adults, and those with high levels of WC during adolescence showed higher BP during adulthood. CONCLUSIONS: The results indicate a significant relationship between adolescent cardiorespiratory fitness and adult body fatness and a lack of an association between adolescent cardiorespiratory fitness and adult cholesterol, BP, and glucose levels. Adolescent body fatness is moderately related to selected adult CVD risk factors.