The article describes the procedures and the specificities that characterized the PS (Public Security forces) purge, which was part of the general attempt of defascification of the Italian State administration. The aim of the article is to trace the diachronic shifts that the PS purges underwent in the period 1944-1952, and to analyze the varied organisms responsible for the purge and their own members. Furthermore, it takes in exam several individual cases during the different stages of the purging trial. In its conclusions, the article suggests that the PS purge was mildly carried out as much as the general attempt of defascification of the Italian state was.