Although the study of self-selected ethnic labels may aid scientists in their understanding of an ethnic group, the uncoordinated use of ethnic labels applied by social scientists and others can result in confusion and misinformation. A literature review yields a plethora of terms used to refer to Mexican Americans. Terms currently popular are Hispanic, Chicano, Mexicano, and Mexican American. One source of data for social scientists has been the government census which has used a variety of identification and classification techniques including objective and/or subjective methods of defining ethnic populations. Many existing terms are too broad or are found to be undesirable by the population to whom the term is applied. The term Hispanic ignores national boundaries. The popular term Chicano refers to a population Mexican Americans perceive as being more ethnocentric, anti-establishment and politically active, but is often used by social scientists without those distinctions. The term Mexican American is most applicable when referring to Americans with ancestral ties to Mexico as it is both descriptive and consistent with terminology presently employed to identify other ethnic groups. Social scientists engaged in Mexican American studies must agree on terminology in order to facilitate comparisons and the accumulation of knowledge. (PM)