The report draws upon two primary sources of information: the FBI Uniform Crime Reports annual "Crime in the United States" volumes and the U.S. Census Bureau "Population Series." The first chapter contains information about the juvenile population during the years 1970-81. The data appearing there provide an essential element for interpreting the remainder of the volume, because they were used in the calculations to produce arrest rates, and because trends in population size are an important policy consideration independent of arrest rates. Chapters II through IV contain aggregate information on the character of juvenile arrests during the report years. Those chapters include gross comparisons of juvenile and adult arrest statistics, proportions of total juvenile arrests among various offense categories, and sex and race differences in juvenile arrests for various offense categories. Chapters V through XI contain arrest-rate trends by age according to such classifications as age; sex; race; and city, suburban, or rural locale. These analyses show fluctuations in the frequency of arrests, standardized for a uniform population base. To permit comparisons of juvenile arrest-rate trends with adult arrest-rate trends, one appendix supplements this report with adult arrest-rate trends for five major offense categories. 12 tables and 48 figures