Focusing on David B. Riazanov career and his pioneering efforts in producing a complete edition of the works of Marx and Engels, the article explains why Riazanov’s variety of Marxism was unacceptable to the Soviet regime, and why from 1924 Lenin was credited with being an outstanding Marxist theoretician, whereas previously he had been regarded only as a skilled political activist. The concept of Leninism as a new stage of Marxism was put forward by Bukharin and elaborated on by Stalin and Zinoviev. Georg Lukács attempted to show that Lenin’s thought had the internal coherence that Bukharin postulated. In support of Lenin’s theoretical credentials, his ‘Philosophical Notebooks’ began to be published from 1925. However, neither Riazanov nor his associate Abram M. Deborin subscribed to the official doctrine that Leninism was a new and higher stage of Marxism. For this stance they fell victim to Stalin’s repression.