Infusion experiments of 10 per cent citrate, citrated blood and heparimated blood were performed on dogs, and results obtained were as follows. 1) Blood pressure tended to drop by citrate infusion and finally became fatal after its rapid drop. Although, the sequelae of citrated blood transfusion were about the same as those of citrate infusion, no drop in blood pressure was observed in heparinated blood transfusion. This drop of blood pressure was caused by citric acid. 2) Pulse rate was decreased parallelly with drop of pressure, respiratory rate was increased with difficulty of breath and tended to decrease later. 3) Circulating blood volume determined by P(32) was increased. 4) On E. C. G. findings, in lead Ⅱ, gradual prolongation of QT and gradual increase of QT/PT, elevation of T-wave etc. were noted. 5) Cardiac output determined by catheterization was decreased but a stroke volume increased, A-V difference of oxygen increased, and peripheral blood vessel resistance decreased, without marked decrease in cardiac function. 6) Causes of rapid drop of blood pressure and death were thought to be due to abnormality of electrolytes in cardiac muscle produced by citric acid infusion.