An introduction describes the study and discusses data collection procedures, file structure, weighting, information processing, and codebook information. Data for the analysis were collected from the records of the Philadelphia public, private, and parochial schools and from the records of the Philadelphia police department's juvenile aid division. Much of the research considered four questions: when the delinquency of a cohort boy first brought him to the attention of the police, whether he desisted from or persisted in committing further delinquent acts, the extent of harm inflicted on the community by his misdeeds, and whether the seriousness of his delinquent activities increased or decreased with age. The data are available in two formats: a card-image file and an OSIRIS data set. A glossary is provided.