The article is devoted to Vilfredo Pareto's reflections on socialism and dicusses thoroughly his important work 'Les syst'emes socialistes', especially its first part dealing with so called real socialist systems. This large treatise edited in 1901-1902 played an important role in the evolution of Pareto's ideas. It brought the early version of his famous theory of social elites that was strictly connected with his refutation of historiosophical progressivism. Pareto examined many historical examples - from ancient Greece to some tendencies in contemporary policy - in order to elaborate the precise typology of the systems of real socialism. He tried to demonstrate that real socialism was an obstacle to economic and cultural development. Socialism was for him on the one hand utopian, and on the other hand - immoral (as the apology of plunder and as a riot against social hierarchy). He didn't exclude however that in the future the well organized socialist movement would come into power.