This report evaluated (a) the temporal stability of hemodynamic responses to three tasks using impedance cardiography, and (b) the influence of aging on stress responses in a multi-ethnic pediatric sample. One hundred children 8 to 10 years old and 49 adolescents 15 to 17 years old were tested at study entry and on average 3 years later. Results showed that the composite task-induced changes in stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR), and pre-ejection period (PEP) were moderately stable across 3 years (rs = .36 to .51), with children showing greater stability in task-induced CO change than did adolescents. However, the magnitude of the participant's stress responses changed over time, varied by task, age group, and gender. These results suggest that hemodynamic responses to stress change with aging during childhood and adolescence and that they can be measured reliably.