The existing studies have had a consensus in that the Cold War was the result of suspicions and conflicts between America and Russia, and the Truman Doctrine was the essential principle of operating the Cold War. But, in the present writer`s opinion, the Cold War was essentially a strategic device to realize America`s hegemony within the sphere of capitalist world. The Truman Doctrine, therefore, must be understood in this context. The intent of this thesis is to make clear the implications of the Truman Doctrine with this perspectives. The following are the consequences of examining the Truman Doctrine. First, the essence of the goals of the Truman Doctrine was to realize America`s hegemony within the capitalist world. At postwar, by their experiences with the Soviets, American leaders perceived that the Russians would not open Eastern Europe. Then, American value of multilateralism should be expanded only within the capitalist world. Second, the major goal of the Truman Doctrine was to accept Russian sphere of influence and achieve mutual co-existence between two great powers as a necessary precondition for America`s hegemony. But, approving `exclusive` sphere of influence of the Soviets in Eastern Europe meant drawing the line to divide Europe and probably evoking sensitive political reverberations. Nevertheless, the United States leaders had no choice but to draw the division line of Europe for their hegemony. It was the best way to rid the Russians of their anxiety for national security and to simultaneously contain them. It was also the best scheme to control and reconstruct the capitalist world. American strategy, of course, rested on the limits of the Russians power and the absence of their aggressive intentions. Third, The Truman Doctrine dramatized the threats of the Soviet Union and communism. In fact, at that time, the United States had no pretense of dividing Europe. Because of the very problem, American officials greatly emphasized the threats of the Soviet Union and communism. So the Truman Doctrine showed the hopeless situation that conflicts between the two countries could not be settled. But the essential problems were `cold` co-existence between America and Russia. In sum, the Cold War did not result from the threats of Russia and communism, but from America`s pursuit of hegemony within the limited sphere of the capitalist world. The cool co-existence between Russia and America was a precondition for America`s goals. And, emphasizing the threats of Russia and communism was a scheme for America`s hegemony. Through the Truman Doctrine, the United States claimed formally America`s position all the world over.