The development of the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1994) included 12 field trials to assess proposed revisions. This article provides results from the antisocial personality disorder (APD) field trial that was conducted to obtain data of relevance to the proposals for simplification and for the inclusion of more traditional traits of psychopathy. Provided herein are the results from 4 sites that had sampled from populations of particular relevance to the diagnosis of APD (i.e., prison inmates, psychiatric inpatients, outpatients with substance use disorders, and homeless persons). The results indicated that some items from the 3rd revised Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1987) could be deleted without affecting the diagnosis. The field trial provided mixed support for the proposal to include more traditional traits of psychopathy.