To critically review the current literature on pathological gambling as regards the significant psychiatric comorbidities associated with it. The authors synthesized information found via electronic searches (MEDLINE) and bibliographic-directed searches in over 60 publications. Pathological gamblers frequently have comorbid substance use disorders. In addition, a subset appear to have comorbid antisocial personality disorder, but they represent a minority when compared with those people who have acquired their antisocial traits as a consequence of their gambling behaviour. A comorbidity with the mood disorders is probable, but methodological concerns and inconsistencies with the data prevent further delineation of this. Emerging research for other disorders possibly associated with pathological gambling is also reviewed. Pathological gambling is associated with significant psychiatric comorbidity. Recommendations for future research are described.