The beginnings of the research career of Oskar Lange were linked with his critical analysis of capitalism. In 1934, aided by Marek Breit, Lange set out to define the mechanism undergoing the functioning of the socialist economy. Two years later, referring to the neo-liberal concepts prevalent at the time and critical of socialism, he presented a decentralized socialist economy model that earned him international acclaim. Lange spent the war years in the United States where he wrote his internationally recognized work on employment and price flexibility. He lectured at several leading U.S. universities and began to perform various social and political functions on behalf of Poland. Another noteworthy period of his career coincided with the beginnings of economic reform in Poland in 1956 and the establishment of an Economic Council under his leadership. Another special moment was the publication of his work on political economics. It raised a lot of polemics and controversy, chiefly because Lange called for the need to include the principle of rational management in Marxist economics. Actually, 20 years later—after Lange’s death—these problems provoked heated disputes. In reference to economic reform, Lange was preoccupied with an analysis of ownership forms and the functioning of various types of enterprises as well as the principles of central planning. Lange’s last article, The Computer and the Market, raised eyebrows among economists in 1965. In this essay, Lange largely revised his previous assessment of the allocation capabilities of the market. Lange was undoubtedly an outstanding scholar who was recognized around the world and contributed to the international reputation of Polish science.