Empirical evidence for the stress and negative affect model of adolescent alcohol use has been inconsistent. We hypothesized that this inconsistent support was partially due to a third variable that moderates the model's effects. The current study assessed behavioral undercontrol as a moderator of the stress and negative affect model of adolescent alcohol use. Using a community-based sample of adolescent children of alcoholics (COAs) and a demographically matched comparison group (non-COAs), life stress, negative affect, behavioral undercontrol and alcohol use were assessed. Results showed that the stress and negative affect model predicted alcohol use. Consistent with theoretical predictions and previous research, negative affect partially mediated the relation between stress and alcohol use. However, behavioral undercontrol did not moderate the effects of stress and negative affect for COAs and non-COAs. Theoretical and methodological implications of the findings are discussed.