Lenin's name has been coupled with that of Marx as the co-founder of the theory of ‘Marxism-Leninism'. However, despite his emphasis on the role of revolutionary theory, Lenin's original theoretical contributions to the development of Marxism were very limited. His talents were those of a determined revolutionary, in the populist tradition of Chernyshevsky, and a brilliantly effective propagandist and political organiser. His contribution to ‘Marxism-Leninism’ was to modify Marxist orthodoxy in such a way as to integrate the political and organisational principles of revolutionary populism into Marxism, on the basis of Plekhanov's ‘dialectical materialism', whose distinctive interpretation of Marxism was Lenin's constant guide and inspiration. In this paper I want to argue that Lenin never broke from the theoretical and political traditions of Russian populism, but completed Plekhanov's project by assimilating Marxism to the very different theoretical framework of populism.