Naltrexone, a prescription medication, was approved in December 1994 as an adjunct to counseling in treatment of alcoholism and alcohol abuse, representing the first new medication for alcoholism in several decades. Initial controlled trials indicated that it is effective in preventing relapse, while later trials show mixed results. Although many physicians and others treating alcoholism have found naltrexone to be very helpful in treatment, it is still a technology that has not been used widely. In this study, we examine which clinicians have adopted naltrexone into practice for what reasons, and what clinical and nonclinical factors acted as barriers to its use. In our mail survey of alcoholism treatment clinicians, 80% of physicians and 45% of nonphysicians report prescribing or recommending naltrexone at least rarely, but only 15% of physicians, even among addiction specialists, prescribe naltrexone often. The strongest barriers to adoption of naltrexone were financing and inadequate knowledge about the medication, followed by lack of sufficient evidence regarding effectiveness. Clinicians were most likely to adopt naltrexone if they were affiliated with treatment programs that actively promoted its use. We conclude that in order for a new substance abuse treatment medication to be widely adopted in clinical practice, information about it must be properly directed, clinicians must be convinced of its effectiveness, it must be adequately financed, and the treatment organizations in which clinicians work must promote its use.