This report provides evidence for the reliability, validity, and developmental course of the psychopathic personality traits (factors) of Fearless Dominance (FD) and Impulsive Antisociality (IA) as assessed by items from the Multidimensional Personality Questionnaire (MPQ; Patrick, Curtin, Tellegen, 2002). In Study 1, MPQ-based measures of FD and IA were strongly correlated with their corresponding composite scores from the Psychopathic Personality Inventory-Revised (Lilienfeld Widows, 2005). In Study 2, FD and IA had relatively distinct associations with measures of normal and maladaptive personality traits. In Study 3, FD and IA had substantial retest coefficients during the transition to adulthood, and both traits showed average declines with an especially substantial drop in IA. In Study 4, FD and IA were correlated with measures of internalizing and externalizing problems in ways consistent with previous research and theory. Collectively, these results provide important information about the assessment of FD and IA.