A review is presented on published equations connecting the cardiac output per minute (COM) with the body weight (BW) in mammals with different BW under the conditions of the relative motor rest. The entire series of these animals with the BW from several grams to many tons is well described by the equation α-BW0.75, in which the α coefficient changes parabolically by increasing to the smallest and largest animals. According to it, the BW increase from 20 g to 70 kg is accompanied by an 8-fold decrease of the specific COM from 72 to 9 ml/min × 100 g. As judged from publications, this COM decrease is accompanied by changes of its interorgan distribution. The volume rate of the blood flow (per 100 g of the organ) is preserved in kidney, decreases approximately 3 times in heart and organs of v. hepatica, remaining higher in heart, and decreases markedly in skin (14 times), in skeleton (18 times), and skeletal muscles (21 times). The mechanisms of such changes of the organ blood flow are different changes of the organ parts of COM and relative body weights of the organs.