The subject of this research is: 1) the prehistory of Bernstein's revisionism, German (and not only German) "catheder-socialists", the English "Fabian society"; Russian Narodism, "legal Marxism"; 2) theoretical views of E. Bernstein, their formation and development; (3) a critique of Bernsteinism by his Marxist contemporaries in the late 19th and early 20th centuries. 4) the development of Bernstein's revisionism by theorists of the social democratic parties of the middle and second half of the XX century . 5) Eurocommunism, or "Western Marxism", as a latent, partly open revision of Marxism and mainly of the so-called Marxism-Leninism . Since the revision of any scientific theory, no matter how high its status, is a normal, generally accepted research procedure, in so far as its qualification is, in principle, incompatible with the teaching of K. Marx and F. Engels is a testimony to the dogmatism inherent in Marxism and the beginning of its dogmatization by Marxist parties. Thus, the concept of "revisionism", scientifically untenable, unacceptable in the scientific environment outside of Marxism, is nothing but a euphemism that covers the ideological isolationism of "scientific socialist ideology" ..