In summary, it can be said that in spite of possible limitations, this technique provides previously unattainable data on capillary flow pattern in the myocardium. Qualitative and quantitative results indicate that the following anatomical and physiological concepts should be incorporated in any further modelling of oxygen transport to myocardium: (1) Concurrent flow pattern (2) Presence of short capillary loops (3) Presence of capillary bundles (4) Staggered arrangements of arteriolar inflow to capillary network.