Data for the study were collected in Seattle, Wash., in 1978-79 through interviews and questionnaires administered to delinquent and nondelinquent youth. The report discusses the content and logic of self-report measures, concentrating on the question of empirical homogeneity among self-report items, and examines the evidence on the reliability and validity of self-report measures of delinquency. The report examines the correlates of delinquency that have received central theoretical and empirical attention: sex, race, socioeconomic status, age, intelligence, delinquency of friends, and school performance. The purpose is to determine whether the results depend on the measure of delinquency employed and, if so, whether the discrepancy can be explained by extraneous differences between the two measures without questioning the ultimate validity of either self-report or official methods of measurement. Findings indicate that in several cases no discrepancy appeared while in other cases discrepancy was easily explained. Further analysis indicates that the self-report method can produce reliable and valid results when applied to white, in-school, and generally not seriously delinquent populations. The self-report method produces less valid results among groups that tend to have high rates of official delinquency -- particularly black males. Thus, investigators must stratify by race in sampling and analyzing self-report data. Other conclusions are detailed regarding methods of administering self-report instruments, instrument and item content, and scoring procedures. Tables, graphs, chapter notes, an index, and about 170 references are included. Study instruments and data, the Short-Nye self-report delinquency items, and other material are appended.