Heroin addiction is one of the most devastating and expensive of public health problems. The most effective treatment is opioid replacement therapy. Replacement of heroin, a short-acting euphoriant with methadone or other opioids that have significantly longer duration of action provides a number of therapeutic benefits. Opioid detoxification has a role in both preventing acute withdrawal and maintaining long-term abstinence. Opioid-based detoxification is based on the principle of cross-tolerance, in which one opioid is replaced with another one that is slowly tapered. For the treatment of heroin addicts a wide range of psychosocial and pharmacotherapeutic treatments are available; of these, methadone maintenance therapy has the most evidence of benefit. Methadone maintenance reduces and/or eliminates the use of heroin, reduces the death rate and criminality associated with heroin use, and allows patients to improve their health and social productivity. In addition, enrollment in methadone maintenance has the potential to reduce the transmission of infectious diseases associated with heroin injection, such as hepatitis and HIV. The principal effects of methadone maintenance are to relieve narcotic craving, suppress the abstinence syndrome, and block the euphoric effects associated with heroin. There is growing interest in expanding treatment into primary care, allowing opioid addiction to be managed like other chronic illnesses. Buprenorphine which is a long-acting partial agonist was also approved as pharmacotherapy for opioid dependence. Opioid antagonists can reduce heroin self-administration and opioid craving in detoxified addicts. Naltrexone, which is a long-acting competitive antagonist at the opioid receptors, blocks the subjective and objective responses produced by intravenous opioids. Naltrexone is employed to accelerate opioid detoxification by displacing heroin and as a maintenance agent for detoxified formerly heroin-dependent patients who want to remain opioid-free.