This chapter traces Marx's influence on the development of the early Frankfurt School, making explicit the Marxist dimensions of its cultural critique, its dialectical, historical, and materialist methods, as well as the role of praxis and class in its critical social theory. The author outlines the general characteristics of Western Marxism and then contrasts them with the deterministic doctrines of the Second International and Soviet Marxism. He then examines the Marxist heritage of the Institute of Social Research's influential and programmatic texts of the 1930s, beginning with Horkheimer's inaugural address of 1931. Although the chapter briefly discusses the work of Institute members such as Henryk Grossmann, Leo Löwenthal, and Erich Fromm, its primary focus is on the work of Max Horkheimer, Theodor Adorno, and Herbert Marcuse.