The analysis of the five studies provides support for a unified theory of antisocial behavior, from childhood aggression to adult criminality. Besides the fact that childhood aggression and adult criminality are dimensional rather than taxonic, there are at least two other points on which the two constructs converge. First, confirmatory factor analyses indicate that two dimensions, “proactive” and “reactive,” do a better job of accounting for childhood aggression and adult criminality than that of a one-factor model and a social-learning model with cognitive and behavioral factors. Second, these two dimensions are highly correlated. The rating scales that have been used to classify children as proactive or reactive have been found to correlate with each other. The two-dimensional model advocated in this article can be considered one level of a larger theory in which aggression and criminality are hierarchically organized, with a general tendency to aggress against others and violate the rules of society at the top of the hierarchy. Below this would be the proactive and reactive functions of aggression/criminality, and below that, the specific attributions, expectancies, goals, values, and thinking styles that facilitate aggression and criminality. Results from the current investigation indicate that the general tendency toward aggression/criminality does not adequately explain the overlap among psychopathy, antisocial personality, and criminal lifestyle, so there is a need to look to lower levels in the hierarchy (proactive, reactive) to gain a better understanding of the relationships between these three crime-related constructs. 9 tables and 79 references