The discussion on the concepts of biological and social factors in the determination of the health-illness process is a basic theme in Public Health in Brazil, and in the epidemiological field. This article presents the results of a qualitative research on the records of Brazilian Epidemiology Congresses in the period between 1990 and 2002. Its objective is to identify the notions of biological and social factors, seeking to recognize the theoretical assumptions underlying them. Results demonstrated that the concept of social factor is mentioned mainly in the sphere of 'societary', anchored in the dissociation between natural and social sciences. The biological factor is associated with the individual and clinical sphere of the health-illness process, seldom attributed to the sphere of collective, and it is perceived as the bearer of the concept of objectivity. In the biological-social relation, the environment appears as an independent category; the biological factor also appears, in an incipient form, as a complex, historical and intrinsically social concept. The analysis pointed toward the need for a theoretical redefinition that could enable the advancement of knowledge in the area, and, consequently, of health practices based on Epidemiology. The research project has been through the Etical Research Committee of the Instituto de Saúde SESSP and was aproved.
Epidemiology; Biological; Social; Social sciences; Natural sciences; Public health