Previous research has found that four subtypes exist in individuals with Antisocial Personality Disorder (ASPD): primary, secondary, "fearful" psychopathic and non-psychopathic ASPD. This study found modest differences between these subgroups in terms of substance abuse, with secondary psychopaths reporting more severe abuse than primary psychopaths. In addition, the study found that the associations between negative emotionality and impulsivity and substance abuse increased across the sample as the subgroup type became more severe in the existence of ASPD. This study investigated whether the rate of substance use and the existence of negative emotionality and impulsivity could determine the extent to which an individual suffers from ASPD. Data for the study were obtained from participants in a substance abuse treatment program (n=571). Individuals identified with ASPD were placed into one of the four clusters and compared to non-ASPD substance abusers in terms of the severity of their self-reported alcohol and drug problems, and whether the severity was predicted by the existence of negative emotionality and impulsivity. Analysis of the findings indicates a strong relationship between substance use and increased degree of ASPD, but while an association exists between negative emotionality and impulsivity and substance abuse, the degree of the association is weaker than predicted. Study limitations are discussed. Figure, tables, and references