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, and to explain why juvenile delinquency began, why it did or did not continue into adult crime, and why adult crime often ended as men reached their twenties. The original sample included over 400 boys who were living in a working-class area of South London, England at the time of the first assessment. They were recruited from six state primary schools in the local area. Their parents and, in later waves, their children, were also included in the study. The original boys are known as generation 2 (G2), while their biological parents are generation 1 (G1), and their biological children are generation 3 (G3). Baseline data collection took place in 1961 to 1962 when the G2 participants were 8 to 9 years old and they were followed up at ages 10, 14, 16, 18, 21, 25, 32, 48 and 70 years. G1 participants and teachers were also interviewed when the boys were aged 8 to 15 years, at the family home or school. Between 2004 to 2013, over 500 G3 participants were interviewed and have been followed up through linked data until 2012.