This conference paper presents the "ethnic matrix," a theoretical model of the process of ethnicity which describes how ethnic identity is sustained or diminished in the life of an individual or ethnic group. After a general introduction, the first of the paper's three major sections presents a research review and overview of historical and societal perspectives of ethnic identity. It argues that, as a response to the cultural preservation revolution of blacks and Hispanic Americans of the 1960's, social scientists attempted to become more sensitive to the complexities of culture. Yet much remains to be understood about the form and function of the acculturation and assimilation process: it can no longer be simply assumed that individuals within a particular ethnic group will ultimately move from immigrant to assimilated Americans. The paper's second section presents the ethnic matrix model. A continuum is said to exist between two opposite poles: complete maintenance and complete assimilation. The individual fluctuates between these poles, and an individual's ethnic orientation is ultimately defined by daily choices, not by a fixed ethnic identity. The final section describes the nature of ethnic choices, and introduces a vertical component to the model, the intensity of the choice's impact on identity. The paper concludes by discussing some of the implications of the model for the social sciences. (KH)