Epidemiology has taken on a prominent role in workplace research. Occupational physicians do not always have all the tools needed to understand the fundamentals of epidemiological studies, participate in them, or even organize them. We will review the principles by outlining the steps involved in conducting a study, from formulating the research question to publication, emphasizing the need to collaborate with specialists in occupational risk epidemiology. We will focus particularly on developing the protocol for an epidemiological study, which outlines all the essential steps. Following an essential literature review, the development of a comprehensive protocol will help clarify the context of the epidemiological study, define its primary objective, and outline the methods used to achieve it. The protocol specifies the type of study, the target population, and the data to be analyzed. It also details the various logistical aspects of the study. Finally, the basics of analysis and interpretation are briefly discussed. The various steps are illustrated with a concrete example. (R.A.)