Using a multimeasure longitudinal research design, we measured psychopathy with the Youth Psychopathic Traits Inventory (YPI) and the Psychopathy Checklist–Youth Version (PCL-YV) among 122 offending girls. We examined the psychometric properties of the YPI, investigated the association between the YPI and the PCL-YV, and assessed their concurrent and longitudinal association with externalizing problems on the Youth/Adult Self-Report and violent and delinquent behaviors on the Self-Report of Offending. Alphas for the YPI were adequate and there were small to moderate correlations between the YPI and PCL-YV, suggesting that each assesses distinctive personality features. The YPI and the PCL-YV were approximately equivalent in their association with concurrent and longitudinal outcomes with two exceptions, where the YPI demonstrated a stronger association with antisocial behavior. Concurrently, there was a divergent relationship between the psychopathy factor scores and antisocial outcomes. Within 2 years, the psychopathy affective factor, which constrained the YPI and PCL-YV to be equivalent, was associated with externalizing behaviors and the YPI affective factor was associated with violent offending. Approximately 41/2 years later, neither measure was significantly related to antisocial behavior after accounting for past behavior. Reasons for continuity and discontinuity in risk identification are discussed.