A new non-invasive method for investigating total coronary blood supply is presented. This method is based on the principle of indicator dilution of a radio-nuclide bolus (99Tc), requiring a scintillation camera with high sensitivity and high picture resolution. The first findings obtained from 83 patients are shown. With 4.61 +/- 1.19% of cardiac output the mean values of the rates of coronary perfusion obtained at rest in subjects with a normal heart differed significantly from those obtained for patients with certain coronary occlusions (8.18 +/- 3.99% of cardiac output) and from those obtained for hypertensive patients (Stages I-III). Double examinations carried out on 20 patients yielded an adequate reproducibility. The mean deviation of the double examinations from one another was 16%.