This paper examines the extent to which conduct problems at age 13 are associated with a range of educational, psychosocial, and sexual outcomes at age 18 in a birth cohort of 488 young women. Significant associations were found between early adolescent conduct problems and later risks of educational failure, juvenile crime, substance abuse, mental health problems, and adverse sexual outcomes by late adolescence. These elevated risks were explained, in part, by social, family, and personal disadvantages associated with adjustment at age 13. In addition, there was evidence of a causal chain process in which early adolescent conduct problems were associated with a series of adolescent risk-taking behaviours, including delinquent peer affiliations, early-onset sexual behaviour, substance use, and school problems that were, in turn, associated with increased risks of later adverse outcomes.