This is the first of a two paft study concerning with concepts such as ethnia, ethnicity and the ethnic group in archaeology, as specifically applied to the Posclassic Period in the Valley of Toluca. This first part focuses on the theoretical aspects of the problem mentioned above. Based on a retrospective analysis, it describes different theoretical perspectives of the concepts related to ethnic problems. Our principal interest is concerned with the approach to undocumented prehispanic ethnic reality on a regional scale, basically through material culture and settlement distribution, obtained from surface suwey. Also, we will propose a hypothesis on ethnogenesis, which will be applied to a case study in the Toluca Valley during the Posclassic Period, a time when a consolidation of multiethnic groups were forming.Esta es la primera parte de dos en que la autora dividió su estudio donde trata los conceptos de etnia, etnicidad y grupos étnicos en Arqueología y aplicados al periodo Postclásico en el Valle de Toluca. En esta primera parte, Sugiura se enfoca en las consideraciones teóricas de estos conceptos y se basa en un análisis retrospectivo que describe diferentes perspectivas teóricas sobre éstos relacionados con problemas étnicos.