Children and adolescents who exhibit a callous interpersonal style seem to be at risk for developing severe forms of violent behavior. Theoretical models suggest that children with low levels of temperamental fearfulness may be at increased risk for developing callous traits because they are relatively unaffected by punishment. This study examines hypotheses about the callousness pathway to severe violent delinquency in a cross-sectional sample of 169 (97=males, 72=females) adjudicated adolescents. Structural equation modeling is used to test mediation models regarding the relation between temperamental fear, punishment concern, callousness, and severe violent delinquency. The findings of the study indicate that the relation between low levels of temperamental fear and increased callousness is mediated by a lack of concern about being punished for aggressive acts. Although low levels of fear and punishment concern were both related to increased levels of severe violent delinquency, increased levels of callousness mediated these relations. All findings remained significant after controlling for the potential confounds of gender, race, and social desirability. The results provide a heuristic for understanding the callousness pathway to severe violent behavior in youth. However, longitudinal investigations replicating these results are necessary before firm conclusions can be drawn. Aggr. Behav. 32:590–598, 2006. © 2006 Wiley-Liss, Inc.