The use of a strategy for the classification of geographical units in the study of marginalization and well-being, supported by a proposed criterion for the search of more homogeneous alternatives, is introduced. The conglomeration method by degree of marginalization, used in Mexico by CONAPO, which is based on the first principal component computed from standardized versions of the selected indicators, is reviewed. In order to solve the identified limitations, the strategy whose use is being proposed obtains alternative classifications based on one or more principal components from the non-standardized indicators. The best classification is then determined using the proposed homogeneity criterion. The application of the strategy is exemplified using municipal information from the II Conteo de Población y Vivienda 2005, in Mexico as used by CONAPO. It is shown that, for this data, the optimal classification of municipalities is reached when only the first two principal components are used.