Inflammatory markers such as C-reactive protein (CRP), fibrinogen, and white-blood-cell (WBC) count are strongly associated with cardiovascular disease. The authors' purpose was to compare the inflammatory response to a single aerobic-exercise session between individuals of high and moderate fitness. Ten apparently healthy highly fit and 11 moderately fit men expended 500 kcal at 70% of VO2peak. Fasting blood samples were obtained on 2 consecutive days before and again at 24, 72, and 120 h postexercise. Blood samples were analyzed for CRP, fibrinogen, and WBC count. CRP was 76% lower at baseline in the highly fit group than in the moderately fit group (P = 0.03). CRP, fibrinogen, and WBC count remained unaltered, however, in the days after exercise (P > 0.05 for all). These findings suggest that markers of inflammation are stable in the days after a single session of moderate-intensity aerobic exercise in apparently healthy men of at least average fitness. © 2007 Human Kinetics, Inc.