The research investigates the changes in the composition and in the role of the Tertiary Sector of the brazilian economy, due to the technological modernization process and to the growing of international globalization. In the first place, it evaluates theoretical aspects about the role of tertiary activities in economic context, as absorbing workers and as providing basic substructure and the necessary complementarity to the development of the other sectors. In sequence, it empiricaly investigates the evolution of the brazilian Tertiary Sector in a comparison with the Primary and Secondary sectors, and also the occupational structure of the services inside and outside the enterprises. Finally, it analyses the regional differences in evolution of the services activites among regions in Brazil.