Antisocial personality disorder (ASPD) and psychopathy are 2 important syndromes with substantial utility in predicting antisocial behavior. Although prior studies have identified correlations between various factors and the presence of psychopathy or ASPD, most studies have focused on 1 syndrome or the other. Consequently, it is unclear whether the 2 syndromes reflect similar pathophysiologies, whether they are in fact 2 distinct syndromes, or whether the correlates of ASPD reflect its high comorbidity with psychopathy. The present study addressed this issue by examining the impact of ASPD with and without comorbid psychopathy (as assessed by the Psychopathy Checklist-Revised) on criminal offending and cognitive processing in 674 adult male inmates at a county jail in Illinois. Participants exhibited either ASPD and comorbid psychopathy, ASPD but not psychopathy, or neither ASPD nor psychopathy. Participants with and without comorbid psychopathy were characterized by more criminal behavior than controls, and inmates with ASPD and psychopathy exhibited more severe criminal behavior than those with ASPD only. In addition, inmates with ASPD and psychopathy exhibited a different pattern of cognitive task performance impairment than those with ASPD alone. Results replicate the findings of Kosson, Lorenz, and Newman (2006) and provide new evidence suggesting that men with ASPD and comorbid psychopathy are characterized by cognitive processing anomalies different from those seen in ASPD without comorbid psychopathy.