This study investigated the predictive validity of youth callous-unemotional (CU) traits, as measured in early adolescence (Grade 7) by the Antisocial Process Screening Device (APSD; Frick & Hare, 2001), in a longitudinal sample (N = 754). Antisocial outcomes, assessed in adolescence and early adulthood, included self-reported general delinquency from 7th grade through 2 years post-high school, self-reported serious crimes through 2 years post-high school, juvenile and adult arrest records through 1 year post-high school, and antisocial personality disorder symptoms and diagnosis at 2 years post-high school. CU traits measured in 7th grade were highly predictive of 5 of the 6 antisocial outcomes-general delinquency, juvenile and adult arrests, and early adult antisocial personality disorder criterion count and diagnosis-over and above prior and concurrent conduct problem behavior (i.e., criterion counts of oppositional defiant disorder and conduct disorder) and attention-deficit/hyperactivity disorder (criterion count). Incorporating a CU traits specifier for those with a diagnosis of conduct disorder improved the positive prediction of antisocial outcomes, with a very low false-positive rate. There was minimal evidence of moderation by sex, race, or urban/rural status. Urban/rural status moderated one finding, with being from an urban area associated with stronger relations between CU traits and adult arrests. Findings clearly support the inclusion of CU traits as a specifier for the diagnosis of conduct disorder, at least with respect to predictive validity. © 2010 American Psychological Association.