In the present study, the authors use police records and self-report data on police contacts for members of a birth cohort, and find a sustantial level of agreement between the two data sources. However, by incorporating data on police contact seriousness and a variety of demographic characteristics, the authors find some evidence of under- and over-reporting by various groups of cohort members. The authors suggest reasons for both the over- and under-reporting by various groups of cohort members. (Author abstract)