We explored the efficacy of the opiate antagonist, naltrexone, as a treatment for pathological gambling. Treatment seeking pathological gamblers (n = 39) (according to both South Oaks Gambling Screen and a screen based on the Diagnostic and Statistical Manual of Mental Disorders) participated into our treatment study during 2009. The subjects were instructed to use 50 mg of naltrexone before gambling or when feeling craving towards gambling. The protocol contained one initial doctor visit with motivational brief intervention. During period that were free of gambling, the subjects were instructed to practice other healthy behavioral alternatives to gambling. The primary outcome measure was the Yale Brown Obsessive Compulsive Scale adapted for Pathological Gambling. The other outcome measurements were the EQ-5D quality of life survey, the Alcohol Use Disorders Identification Test, and the Beck Depression Inventory. The average age of the subjects was 39 years; 80% were men. Highly significant (p