The flow mechanics of the right coronary system were studied in anesthetized open-chest dogs. The right coronary system fitted the intramyocardial pump(IMP) theory, and the IMP value was 19.3±3.7mmHg. This value was lower than that of the left coronary system found by Spaan. Total resistance of the right coronary system was 1.0±0.4mmHg/ml/100g RV. When the total resistance was assumed to be the sum of two components of resistance, one component (Rp) was proximal to the intramyocardial capacitor (Cim) and the other (Rd) was distal to Cim, the relationship between Rt and Rp was : Rt = 0.36Rp + 0.10 (r>0.88). The time constant of the right coronary system was 2.4±0.8 sec, and the capacitance of the right coronary system was calculated to be 0.074±0.024 ml/mmHg/100g RV. This capacitance was as large as that of the left coronary system reported by Spaan. In summary, the right coronary system had a large capacitance, so that the resistance of the right coronary system did not change throughout the cardiac cycle as in the left coronary system showed by Spaan. However, the flow mechanics of the right coronary system differed from the left quantitatively.