 Despite the well-established efficacy of naltrexone, there are significant variations in individual responses to naltrexone. A critical question remains: under what circumstances and for which patients will naltrexone be most beneficial? Recent work at our center provides evidence that the mu-opioid receptor OPRM1 gene polymorphism A118G Asn40Asp imparts a significant change in treatment response. We have shown that patients with Asn40 variant absence of heavy drinking -73.9 vs 49 response. To further consolidate our knowledge, we wish to test the relationship between A118G polymorphism and the subjectiveobjective measures to alcohol among alcoholics treated with naltrexone. This work is focused on subjects of European or Asian decent as the A118G polymorphism occurs in less than 1 of those of African decent. 