Scant research has examined the validity of instruments that permit observer ratings of psychopathy. Using a nonclinical (undergraduate) sample, the authors examined the associations between both self- and observer ratings on a psychopathy prototype (Psychopathy Q-Sort, PQS) and widely used measures of psychopathy, antisocial behavior, and negative emotionality. Self- and observer prototype correlations generally displayed predicted patterns of convergent and discriminant validity for the PQS. Future research using the PQS should focus on potential domains of incremental validity of peer-rated psychopathy beyond self-reported psychopathy. (Contains 2 tables and 1 endnote.)