The ability of the heart to function as a pump can be assessed by a variety of techniques. Cardiac catheterization, heart-lung preparations, isolated hearts, ventricular wall strips, interventricular septal preparations, and isolated papillary muscles represent only a few of the methods and models whereby cardiac contractile force generation may be directly monitored in an invasive manner. In the interest of clarity, the discussion of cardiac pump function will be divided into subsections of research data obtained from human studies and animal studies. The majority of investigations on cardiac function in diabetic patients have used systolic time intervals as a measure of cardiac performance. The application of systolic time interval measurements to cardiac performance in diabetes has revealed significant defects in almost all of the values. Radionuclide angiography has also been employed to assess cardiac performance in control and diabetic patients. Myocardial performance is assessed by first-pass radionuclide angiography or gated blood-pool equilibrium techniques.