Given increasing awareness of the extent to which environments typically faced by ethnic groups differ, environmental influence on these processes may be an important factor that is an aspect of ethnicity. Socioeconomic status (SES) is a useful index of such environments and is associated with cardiovascular disease (CVD). Since behavior is one pathway through which SES influences are thought to be expressed in disease, this study focuses specifically on stress responsivity, which is thought to be linked to the pathophysiology of CVD. Since such disease has its antecedents in childhood, a multiethnic pediatric sample is employed. In addition, the subject sample consists of twins. Investigation of the impact of environments on the expression of CVD can be achieved only with proper control for biological influences.