The Italian historiography often uses the concept of «anomaly» to characterise the history of Italian socialism after the Second World War. It ascribes to 1947 turning point, i.e. to the choices made that year by Italian socialists in the national and international fields, the reasons for a cultural and organizational «delay» that could explain its subordination and its inability to dominate the Left and, after all, the PSI’s crisis in the Nineties. The present study, through a comparison with the French historiography, intends on one hand to discuss this concept of «anomaly» and the would-be «exceptionality» of Italian socialism in the post war period and, on the other hand, to discuss the role of 1947 turning point in the evolution of the two parties.