Drug abuse and HIV/AIDS are serious global health problems. Injection drug use is currently the major mode of transmission of HIV in many countries. The purpose of this study is to determine the effectiveness of drug and risk reduction counseling combined with either substitution drug treatment with buprenorphine/naloxone (BUP/NX) or short-term detoxification with BUP/NX in preventing HIV transmission among injection drug users. Participants will be recruited for this study in China and Thailand.