Studies report that more female substance users meet the adult antisocial behavioral (AASB) criteria of antisocial personality disorder (ASPD) without having conduct disorder. We assessed gender and antisocial syndrome (ASPD vs. AASB) effects jointly on multiple outcomes in injection drug users. More males had ASPD (40%) and more females had AASB (67%). After adjusting for gender, the ASPD group was consistently more severe, indicating discriminative validity for the diagnosis. However, the AASB group reported substantial pathology, signifying AASB as an important sub-threshold antisocial syndrome. Antisocial behavior might be described as a distribution, with AASB and ASPD defined by increasingly extreme points.