Urbanization is sometimes defined as a process of population concentration that requires both growth in the size of cities and multiplication of their numbers. This demographic approach seems to neglect two other important aspects of urbanization: namely, economic and social. The economic dimension consists of structural change in the productive forces, which include specialization and the division of labor; and the social aspect entails modernization and noneconomic transformations. A suitable definition of urbanization must take all these processes into account. In this report, all aspects will be considered, with an emphasis on objectivity. [For related documents in this series, see UD 013 731-UD 013 741 and UD 013 743-013 744 for surveys of specific countries. For special studies analyzing urbanization in the Third World, see UD 013 745-UD 013 748.] (Author/SB)