The present article is an attempt to organize some information about the history of Epidemiology, in order to understand its evolution as a scientific discipline connected with the historical development of major social movements in the health fields. The roots of Epidemiology from the triad Clinics-Statistics-Social Medicine, its initial development depending on the Public Health, its Technical advancement and ideological constitution within the preventive project, are all discussed. Finnally, modem Epidemiology is seen as a discipline that recovers its historical and roots through the movement of Collective Health, in opposition, at a theoretical level, to pressures to make it a mere "methodological" tool for clinical research.