The seven clusters identified are "internalizing youth A" (withdrawn, abused, and rejected); "socially deprived" (social deprivation and inadequate socialization); "low-control" (high impulsivity, low empathy, aggression, and low remorse); "normal" (accidental, situational delinquent behavior); "internalizing youth B" (internalizing pattern similar to "A" group, but with stronger negative cognitive attributions, mistrust, and hostile aggression); "low-control B" (early onset, versatile offenders with multiple risk factors); and "normative delinquency" (relatively normal social and economic advantages but antisocial behaviors related to drugs, sex, and peer-group associations). Although Moffitt's two main categories of delinquents are evident, several additional stable subtypes emerged that closely resemble Lykken's sociopathic neurotic-internalizing and "normal" types; however, boundaries between delinquent types were not precise and were unstable, and many unclassified cases existed. The first sample consisted of juvenile offenders (n=1,572) from 3 State systems. Multiple cluster analysis methods were applied (Ward's method, standard K-means, bootstrapped K-means, and a semisupervised pattern recognition technique). Core or exemplar cases were identified with a voting procedure. Internal validation was assessed by cross-method verification. External validation assessed type differentiation on several delinquent behaviors. Generalizability was assessed by repeating the clustering on a large replication sample (n=1,453) from another State. 4 tables, 1 figure, 75 references, and appended study instrument and equations