We examined the subsequent criminal activities of delinquent boys classified as having either socialized conduct disorder, undersocialized conduct disorder, aggressive type, or undersocialized conduct disorder, unaggressive type. A follow-up study of more than ten years revealed profound differences in the likelihood of criminal convictions or incarcerations between socialized and undersocialized delinquents. The socialized delinquents have less chance of being either convicted of a crime or being imprisoned. This difference supports the previous studies that demonstrated that these classifications could be distinguished on the basis of differences in behavior, personality, psychological test results, and characteristic family backgrounds, and reinforces this method of classifying conduct disorders. Differences between the undersocialized aggressive and unaggressive groups appear qualitative and indicate that subjects in the former group are involved in more crimes of violence subjects in the latter.