The paper is concerned the concept of ideology in Karl Marx. This concept is historically identified with the formulation of false consciousness. In this paper we will show that, in addition, the concept of ideology in Marx has several functions that are not reduced to a denunciation of deceit and social alienation. Faced with a detailed study of several passages of his work can be inferred that the use of the concept of ideology is not confined to the false consciousness. The question is open, then on the unitary conception of the concept of ideology or if there are several meanings of the term and what role within the Marxian theory.