Technical Abstract: Objective: Cardiovascular reactivity is associated with carotid artery intima-media thickness as early as childhood. Excess cardiovascular responses relative to the metabolic demand during psychological stress have been proposed as a mechanism for this association. It is not known whether measures of excess cardiovascular responses correlate with carotid artery intima-media thickness or mediate the relationship between traditionally measured cardiovascular reactivity and carotid intima-media thickness. Methods: Fifty-four adolescents, ages 13-16 years completed a graded exercise test on one day and measures of psychological stress reactivity (star tracing, speech) on another day. Heart rate, systolic blood pressure, and oxygen consumption were measured on both days. On a third visit adolescents completed an ultrasound scan to measure carotid artery intima-media thickness. Results. Traditionally measured systolic blood pressure reactivity (ß=0.001, p<0.04) and excess systolic blood pressure (ß=0.001, p<0.04) during the speech task were associated with greater carotid artery intima-media thickness. When excess systolic blood pressure was tested as a mediator in the regression model, traditionally measured systolic blood pressure reactivity remained a significant predictor of carotid artery intima-media thickness. Conclusions. This study adds to the growing body of literature showing a link between systolic blood pressure reactivity to acute psychological stress and carotid artery intima-media thickness in youth. Excess systolic blood pressure did not statistically mediate the relationship between traditionally measured systolic blood pressure reactivity and carotid artery intima-media thickness.