The authors examined the construct and incremental validity of the Interpersonal Measure of Psychopathy (IM-P), a relatively new instrument designed to detect interpersonal behaviors associated with psychopathy. Observers of videotaped Psychopathy Checklist-Revised (PCL-R) interviews rated male prisoners (N = 93) on the IM-P. The IM-P correlated significantly with the PCL-R total score. Moreover, the IM-P was preferentially related to the interpersonal rather than the affective and antisocial lifestyle features of psychopathy. IM-P scores were significantly correlated with age, antisocial behaviors, and self-reported fear, anxiety, and socialization (in reverse). Hierarchical multiple regression analyses demonstrated that although the IM-P exhibited incremental validity beyond the PCL-R total score in detecting self-reported fear, anxiety, and several personality traits, it did not exhibit much incremental validity beyond PCL-R Factor 1. These findings raise questions concerning the unique assessment contribution of the IM-P beyond PCL-R Factor 1. Potential reasons for these findings and alternative means of enhancing the interpersonal assessment of psychopathy are discussed. (Contains 3 tables.)