The Cambridge Study in Delinquent Development (CSDD) is a prospective longitudinal cohort study of 411 males living in South London, first assessed in 1961. The original aim of the CSDD was to describe the development of delinquent and criminal behaviour in inner-city males, to investigate to what extent this could be predicted in advance, why juvenile delinquency began, and why it did or did not continue into adulthood. The focus was also on continuity in behavioural development, on the effects of life events on development, and on predicting future behaviour. The study was not set up to test any one particular theory of delinquency but aimed to test many different hypotheses about the causes and correlates of offending.