The Project on Human Development in Chicago Neighborhoods (PHDCN) was a large-scale, interdisciplinary study of how families, schools, and neighborhoods affect child and adolescent development. One component of the PHDCN was the Longitudinal Cohort Study, which was a series of coordinated longitudinal studies that followed over 6,000 randomly selected children, adolescents, and young adults, and their primary caregivers over time to examine the changing circumstances of their lives, as well as the personal characteristics, that might lead them toward or away from a variety of antisocial behaviors. Numerous measures were administered to respondents to gauge various aspects of human development, including individual differences, as well as family, peer, and school influences. One such measure was the Substance Use Follow-Up instrument. It was adapted from the Composite International Diagnostic Interview (CIDI) and was administered to subjects in Cohorts 15 and 18. It obtained information regarding the subject's use of specific drugs. It is closely related to PROJECT ON HUMAN DEVELOPMENT IN CHICAGO NEIGHBORHOODS (PHDCN): SUBSTANCE USE, WAVE 1, 1994-1997 (ICPSR 13602), PROJECT ON HUMAN DEVELOPMENT IN CHICAGO NEIGHBORHOODS (PHDCN): SUBSTANCE USE, WAVE 2, 1997-2000 (ICPSR 13659), and PROJECT ON HUMAN DEVELOPMENT IN CHICAGO NEIGHBORHOODS (PHDCN): SUBSTANCE USE, WAVE 3, 2000-2002 (ICPSR 13743).