Abstract: Traits characteristic of type I and type II alcoholism are thought to relate to dysregulated central nervous system serotonin functioning. In this review, we discuss variables associated with high adolescent alcohol consumption and other risk-taking behaviors in a nonhuman primate model. Adolescent primates with low CSF concentrations of the serotonin metabolite 5-HIAA are more impulsive and exhibit increased levels of alcohol consumption. Both genetic and environmental factors contribute to alcohol-seeking behavior in adolescent macaques. Sequence variation within serotonin system genes, for example, a repeat polymorphism in the transcriptional control region of the monoamine oxidase gene (MAOA-LPR), increases the propensity for adolescent males to consume alcohol. Environmental factors, such as early life stress in the form of peer-rearing or early age of exposure to alcohol, are also associated with increased alcohol consumption. Peer-reared females, especially those exposed to alcohol during early adolescence, exhibit increased rates of alcohol consumption compared to those exposed to alcohol later in development. When genetic variables are also considered, there is an interaction between the low activity serotonin transporter gene promoter s allele (rh5-HTTLPR) and rearing condition on alcohol preference in females but not males, suggesting that the interactions between genes and the environment may be sexually dichotomous. By learning more about the interactions between genes, early experience, and alcohol intake in the adolescent nonhuman primate, we may be able to identify factors that contribute to the susceptibility, pathogenesis, and progression of impulse control disorders, such as alcoholism.