Until positive results were found with oral naltrexone, no medication has been effective against amphetamine dependence. The primary aim of this pilot study is to replicate the findings of the Swedish team that showed oral Naltrexone prevented relapse to amphetamine addiction and to extend their results by randomizing treatment-seeking amphetamine addicted patients to a 6 month course of VIVITROL (naltrexone for extended-release injectable suspension) or VIVITROL placebo. Patients in each group will receive drug counseling. VIVITROL is administered monthly and may be a better test of efficacy than tablets that must be taken daily.