E. Hughes as a professor of sociology in the University of Chicago during the 1950’s developed the study of service occupations while the conventional sociology focused rather on industry and the professions. This article evokes the conceptions of Hughes and examines how these conceptions were enlarged and reinforced in the field works of Gold and Becker on the janitors, the school teachers and the jazz musicians : the comparison of humble occupations and prestigious professions, the conflict of interest and perspective between service workers and clients, the relationship between service institutions and the environing society and especially the weight of the class differences. Returning to this innovative research on service occupations permits to sketch a sociology of work in the service sector, very different from the sociology of the service relationship which has flourished in France since the late 1980’s and which refers mainly to Goffman.