When the May Fourth Movement took place, the Chinese Communist Party (CCP) had not yet come into existence. However, some active participants in the movement later joined the CCR. The most important among them were Chen Duxiu and Li Dazhao. Mao Zedong and Zhou Enlai also played key roles in the movement. On the eve of the May Fourth Movement, Chen Duxiu strongly advocated democracy, science, and a new instrument of political reform-new arts. These were the main content of Xin Qingnian (New Youth) and the New Culture Movement. At that time, his writings showed almost no trace of Marxism. Li Dazhao is regarded as the first propagator of Marxism in China. However, although accepting, with some reservations, Marx's economic theories, Li consistently emphasized mutual assistance and doubted Marx's assertion that utopia could emerge only through class struggle. He thought that this socialist ethics needed to he revised. Mao Zedong played the role of a supporter in the May Fourth Movement. As his activities were concentrated in Hunan Province, he had limited influence on China as a whole. What he advanced had little to do with Marxism and much more for anarchism. Zhou Enlai played a regional role in the May Fourth Movement for pure patriotism. At that time, his thoughts fully reflected the content of the movement-nationalism and democracy. There was no evidence to show that he tried to link Marxism with this patriotic movement. Some participants of the New Culture Movement, the May Fourth Movement in a broad sense, had some knowledge of Marxism. However, in that period when many different theories coexisted, people often supported several political beliefs at the same time. Some people who accepted Marx's materialist conception of history still rejected Marxism's most important principle-class struggle. Thus, these people should not be regarded as Communist intellectuals and it is inappropriate to say that anti-nationalist proletarian ideology took the lead in the patriotic May Fourth Movement.