This study examined the well-being of adolescents before and after a parental divorce. The sample consisted of adolescents who were administered self-report measures of psychological adjustment and substance use over a 5-year period. 48 adolescents experienced the disruption of their parents' marriage during this time. Data were available at an average of 12 months before the separation and 5 months after the divorce. The control group consisted of the 578 adolescents in the original sample whose parents remained continuously married. The most important finding was a striking gender difference in the timing of the effects of divorce, with boys demonstrating ill effects after the divorce but not prior to the separation, and girls showing negative reactions prior to the separation but not becoming worse after the divorce.