This article summarizes the results of a research study on persistent young offenders. It particularly addresses the question of how to define persistent offending, and looks at the consequences of taking different definitions. Using information from the police, from social services departments, and from young offenders themselves, the research considers the nature and extent of offending by young people who are frequently in trouble with the police. It addresses the question of whether or not there is a relatively small number of young offenders who, because of their persistent involvement in criminal activities, account for a large proportion of the offenses committed by young people. The project also examines the background of frequent offenders, their families, educational experiences, contact with welfare agencies and drug use. The study was conducted in two parts: an analysis of the offending patterns, and experience of criminal justice, of a sample of young offenders, all of whom had been arrested three times or more in the course of 1992; and an attempt to define and identify persistent young offenders who had only committed a relatively small number of offenses in the year. Findings are presented. References