This study reports the development of a measure of narcissism within the National Longitudinal Study of Adolescent Health (Add Health) data set. In Study 1, items were selected from Wave III to form the Add Health Narcissism Scale (AHNS). These were factor analyzed, yielding a single factor comprised of five subscales. We correlated the AHNS and its subscales with constructs within Add Health known to be associated with narcissism. Finally, we used the scale to replicate the relationship between narcissism and violence. In Study 2, a separate sample completed the AHNS, as well as other measures, including the Narcissistic Personality Inventory. These studies confirmed that the AHNS is a valid measure for use in narcissism-related studies employing the Add Health data. (Contains 9 tables and 1 figure.)