Many individuals with a history of pathological gambling (PG) also have a history of engaging in antisocial behaviors, and this has often been interpreted as a result of the former causing the latter. In a sample of 7,869 men in 4,497 twin pairs from the Vietnam Era Twin Registry, the authors examined (a) the association between PG and antisocial personality disorder (ASPD), (b) the extent to which PG might be differentially associated with childhood conduct disorder (CD) and adult antisocial behavior (AAB), and (c) the contribution of genetic and environmental factors to the association of PG with ASPD, CD, and AAB. PG was significantly associated with all 3 antisocial behavior disorders, and the association of PG with ASPD, CD, and AAB was predominantly explained by genetic factors. The results of this study suggest that the greater-than-chance co-occurrence of PG and antisocial behavior disorders is partially due to their sharing a common genetic vulnerability. The antisocial behavior observed among many individuals with PG probably cannot be interpreted as being simply a consequence of the PG.