Obesity currently affects 15% of the adolescent population in the United States. To combat obesity and its comorbidities research has begun to focus on adipose tissue. Adipose tissue is now known to secret hormonally active substrates called adipokines. A key adipokine related to obesity and CVD is adiponectin. Adiponectin has anti-atherogenic, anti-inflammatory, and insulin sensitizing properties. In the current study the influence of physical activity on adiponectin was investigated. Through the use of three distinct groups of young males; cross country runners, a normal weight group, and an overweight group. Therefore, the purpose of this study was to identify an independent relationship between habitual physical activity and adiponectin in young men. Thirty-eight young males, 12-21 years of age, were separated into 3 groups; runners, normal weight, and overweight. The normal weight and overweight were determined by BMI. Descriptive data included standard anthropometric variables and peak VO2. Habitual free-living physical activity was assessed with a uniaxial accelerometer worn for four days with one weekend day. Time spent in moderate physical activity (3-5.9 METS) (MPA) and vigorous physical activity (>6 METS) (VPA) were determined based on age-specific cut-points. Blood collection was used to measure serum adiponectin via an enzyme-linked immunosorbent assay. Statistical analysis consisted of ANOVA, ANCOVA, and partial correlations. Age, vigorous physical activity, total physical activity (expressed as counts per minute), and peak VO2 were significantly higher in the runner group compared to normal weight and overweight groups. Similar BMI and body fat measures were identified between runners and the normal weight groups. ANCOVA controlling for age and fat mass showed no significant difference in adiponectin between groups (7.43[Mu]g v. 4.93[Mu]g v. 4.81 [Mu]g). Partial correlation between VPA, PAcnts/min and adiponectin were low and not statistically significant. Inter-relationships between vigorous physical activity, peak Vo2, fat mass, and adiponectin examined by partial correlations failed to identify significant relationships between any variables. The results of this study indicate increased fasting plasma adiponectin is accompanied by large amounts of vigorous physical activity, high peak Vo2 and low fat mass. This study has identified a complex relationship between vigorous physical activity, fat mass, VO2 peak and adiponectin.