The cross-sectional study will determine whether an impairment of the myocardial perfusion reserve provides a marker of coronary heart disease (CHD) by comparing it to other novel measures of subclinical vascular disease, and by testing its association with risk factors for CHD. The study is ancillary to the Multi-Ethnic Study of Atherosclerosis ("MESA"), which is an NHLBI funded, prospective observational study of the characteristics of subclinical cardiovascular disease, i.e. disease detected non-invasively before it has produced signs and symptoms. In MESA new measures of subclinical disease such as coronary artery calcium and impaired brachial artery reactivity are to be examined to investigate their relationships to well-established risk factors and clinical events. Myocardial perfusion reserve (MPR)is a useful measure of coronary vasofunction that should be included in an evaluation of new measures of subclinical disease. An impaired MPR appears to be a specific early indicator of the functional impairment of the microcirculation in patients with risk factors for coronary artery disease. Magnetic resonance imaging (MRI) will be used as an advanced, quantitative imaging modality to determine in short (20 minute) exams the myocardial perfusion reserve in a group of 400 MESA participants. The study tests the hypothesis that impaired myocardial perfusion reserve indicates the presence of subclinical coronary atherosclerosis and coronary microvascular disease.