The article aims to address the relationships between the Italian Marxism and the peripheral nationalisms, through the reading of a political history that has its roots in the Cologne Congress of the Communist Party of Italy, and that continued silently until the dissolution of “Democrazia Proletaria”. The program of action adopted in Cologne in 1931, which contemplated the creation of the federation of socialist and sovietic republics of Italy, declared the beginning of a troubled and ambiguous relationship between our national Marxism and the right of self-determination. Immediately after being set aside by the official Communist movement, this issue remerged periodically in the debates of the revolutionary left. From the relationships between “Lotta Continua” and “Potere Operaio” with the Basques and the Irish separatists, to the formal and official recognition by “Democrazia Proletaria” of the Italian peripheral nationalities, there are many elements which call for careful reflections on these issues. The analysis of the political decisions and the struggles waged in the name of self-determination by the New Italian Left could allow a greater understanding of the complex relationship between Socialism and Nationalism that has been too often misunderstood