Adolescent alcoholics in treatment were classified into two broad clusters. The larger group consisted of youth who demonstrated behavioral dyscontrol and hypophoria, whereas the smaller group consisted of individuals with primarily negative affect. These two clusters differed with respect to age of first drug use, age of first substance abuse diagnosis, severity of substance use, behavior disturbance, and psychiatric disorder. Difficult temperament loaded on the negative affect factor. In a second study, it was observed that difficult childhood temperament led to a number of different first diagnoses in the adolescents. No specific psychiatric outcome followed a difficult temperament. These results illustrate the heterogeneity of the adolescent alcoholic population and suggest that there are many developmental pathways to this outcome where a predisposing risk factor is a difficult temperament makeup.