In the past, evaluation of the myocardium has been limited to examining systolic function of the heart. Recently, however, investigators have demonstrated that abnormalities of diastolic function of the heart provide important contributions to the signs and symptoms experienced by patients with heart disease. In addition, abnormalities of diastolic function may precede abnormalities of systolic function in the early stages of disease. Diastolic filling of the heart, however, is a complex sequence of interrelated events. In order to understand diastolic function, each of these factors contributing to filling of the heart must be examined. They include relaxation, passive compliance, atrial contraction, erectile effect of the coronary arteries, viscoelastic properties, ventricular interaction, and pericardial restraint--all of which are interrelated. In addition, diastolic factors are affected by changes in loading conditions and contractility, and they demonstrate nonuniformity in time and space. This report provides an overview of these various factors from the clinical perspective, based on studies involving the isolated papillary muscle and the isolated heart as well as basic clinical studies.