Information from the 1980 U.S. Census concerning population size and geographic distribution of more than 100 ancestry groups in the United States is presented in this unique reference report. The general ancestry question was based on self-identification, provided no prelisted categories, and allowed for one or more ancestry responses. This was the first census to collect ethnic data on persons regardless of the number of generations removed from their country of origin. The report states that ethnic questions based on self-identification are subject to certain response problems. A section describing limitations on the 1980 census data on ancestry is included. The results of the 1980 census show that English and German were the most frequently reported ancestry groups. This document will be of interest to educators because it provides baseline ancestry figures for a large number of ancestry groups for each state of the United States. These figures may be extrapolated for school populations. Tables of statistical data comprise the body of the report. Definitions and explanations of the various concepts and categories used in the report are provided. An appendix in which the accuracy of the data is examined is also included. (DB)