This article compares different proposals for the implementation of the concept of social class and analyzes the alternatives used in each proposal, considering previous epidemiological studies on this issue and the potential of such a concept as a central category in studies on social determination in the health/disease process. Seven basic differences were identified, pertaining to the following aspects: class structure; research objective; the social class concept as a reference; the decision as to which individual has his/her occupational activity taken as defining the family's social class; the class status of the unemployed, housewives, and the retired; class status of students; and criteria for distinguishing between the "bourgeoisie", "petty bourgeoisie", "new petty bourgeoisie", and "proletariat" and whether there is a specific flow in certain population groups. Given the observed differences and underlying theoretical models, this study discusses problems related to the fact that the use of a specific concept of social class can have various implementation models.