431 children (233 boys, 198 girls) born in Stockholm, Sweden, had a detalled behavioral assessment at 11 years of age, including a detalled interview with their school teachers, and at age 27 years were reevaluated to identify alcoholism or alcohol abuse. Specific predictions from a neurobiological learning theory about the role of heritable personality traits in susceptibility to alcohol abuse were tested in this prospective longitudinal study. Three dimensions of childhood personality variation were identified and rated without knowledge of adult outcome. These three dimensions (novelty-seeking, harm avoidance, and reward dependence) were largely uncorrelated with one another, and each was predictive of later alcohol abuse. Absolute deviations from the mean of each of the three personality dimensions were associated with an exponential increase in the risk of later alcohol abuse. High novelty-seeking and low harm avoidance were most strongly predictive of early-onset alcohol abuse. These two childhood variables alone distinguished boys who had nearly 20-fold differences in their risk of alcohol abuse: the risk of alcohol abuse varied from 4 to 75% depending on childhood personality.