Thirty spouse pairs were recruited for a stress protocol consisting of alternating stress and relaxation periods. Repeated measurements of blood pressure, heart rate, and blood volume pulse were obtained. Spouse pairs were parents of young adult sibling pairs who had previously participated in a slightly different version of the protocol. Although spouses exhibited some behavioral similarities, there were no significant similarities in cardiovascular response to stress. However, despite the fact that parents and their offspring were tested on different occasions using somewhat different procedures, some similarities in cardiovascular reactivity were observed. Significant parent-offspring similarities in heart-rate response to mental arithmetic and diastolic blood pressure response to isometric hand-grip were observed, as well as several behavioral similarities. Assortative mating and the nature of one's current home environment seem to be less important in the familial aggregation of cardiovascular reactivity to stress than early environmental and/or genetic factors.