The effect of heterogeneity of capillary spacing on myocardial oxygenation was estimated for various sizes of tissue cylinder radii ranging from 8 to 18 microns, which are the values expected from the histological measurements. Similarly, the effect of mismatching between myocardial oxygen consumption and capillary blood few was analyzed. The results are summarized in charts which demonstrate that both heterogeneities are important independent tissue oxygen determinants irrespective of the mean values of these parameters. Therefore they should be included in any future evaluation of the oxygen supply to tissue.