The role of pharmacologic stress will be assessed by comparison with exercise stress, in order to validate its use in subjects unable to exercise and identify gender related differences. Quantitative measures of regional wall motion obtained from tomography will be compared to regions of prior myocardial infarction (if present), and with other modalities for evaluating cardiac structure and function. The diagnostic and prognostic value of tomographic wall motion analysis will be studied in patients with myocardial ischemia, with special emphasis on correlation between physiologic variables of coronary blood flow and metabolic function.