This article reports on a longitudinal test of a developmental model of early drinking that specifies transactions among personality, learning, and behavior in the risk process. The model was tested on 1,906 children making the transition from elementary school to middle school across 3 time points: the spring of 5th grade, the fall of 6th grade, and the spring of 6th grade. In a transaction that has been referred to as acquired preparedness, individual differences in the trait positive urgency at the end of 5th grade were associated with increases in expectancies for social facilitation from alcohol at the start of 6th grade, which then predicted drinker status at the end of 6th grade. In addition, the alcohol expectancy and drinker status predicted each other reciprocally across time. Multiple factors appear to transact to predict early drinking behavior.