Background- Cardiovagal baroreflex sensitivity (BRS) declines with age but is favorably modulated by habitual aerobic exercise. We tested the hypothesis that compliance (transducing capacity) of an elastic artery in which baroreceptors are located is associated with these age-exercise interactions. Methods and Results- Nine young (28+/-1 years old) and 9 older (65+/-1) sedentary and 10 young (27+/-1) and 9 older (63+/-2) endurance-trained healthy men were studied. Cardiovagal BRS was assessed conventionally (R-R interval-systolic blood pressure [SBP] relation) by the Oxford technique. Because of age-associated increases in central arterial stiffness, cardiovagal BRS was expressed with both peripheral (Finapres) and central (applanation tonometry) SBP values. The change in carotid artery end-systolic lumen diameter (ultrasonography) per unit increase in SBP and the slope of the R-R interval-carotid artery diameter relation also were determined. Cardiovagal BRS declined with age in both sedentary ( approximately 65%) and endurance-trained ( approximately 40%) men but was higher in endurance-trained than sedentary older men regardless of the SBP values used (all P<0.05). Changes in carotid artery lumen diameter per unit increase in SBP mirrored these differences in cardiovagal BRS (all P<0.05). Thus, R-R interval prolongation per unit increase in carotid artery diameter was not different among the groups (P>0.70). Conclusions- These results demonstrate that age- and habitual exercise-related differences in cardiovagal BRS are associated with corresponding differences in carotid artery compliance among healthy men.