Research on psychopathology has been hindered by persisting difficulties and controversies regarding its assessment. The primary goals of this set of studies were to (a) develop, and initiate the construct validation of, a self-report measure that assesses the major personality traits of psychopathy in noncriminal populations and (b) clarify the nature of these traits via an exploratory approach to test construction. This measure, the Psychopathic Personality Inventory (PPI), was developed by writing items to assess a large number of personality domains relevant to psychopathy and performing successive item-level factor analyses and revisions on three undergraduate samples. The PPI total score and its eight subscales were found to possess satisfactory internal consistency and test-retest reliability. In four studies with undergraduates, the PPI and its subscales exhibited a promising pattern of convergent and discriminant validity with self-report, psychiatric interview, observer rating, and family history data. In addition, the PPI total score demonstrated incremental validity relative to several commonly used self-report psychopathy-related measures. Future construct validation studies, unresolved conceptual issues regarding the assessment of psychopathy, and potential research uses of the PPI are outlined.