Pharmacotherapy of intravenous opioid abusers has taken on increased urgency with the acquired immunodeficiency syndrome (AIDS) epidemic, because in major cities intravenous drug abuse now accounts for half of new AIDS cases. The pharmacotherapy of acute dependence and withdrawal has benefited from the use of clonidine, particularly in combination with antagonist-precipitated withdrawal. However, protracted abstinence and its associated risk of relapse to drug abuse has underscored the need for maintenance pharmacotherapies. Maintenance pharmacotherapies such as methadone and naltrexone are frequently needed to sustain outpatient retention and abstinence from heroin. Methadone is more widely used than is naltrexone, an oral, long acting heroin blocker that can maintain drug abstinence after detoxification. Because of limitations in both of these maintenance agents, two investigational maintenance treatments have been tested: levo-alpha-acetylmethadol (LAAM), a long-acting form of methadone, and buprenorphine, a long-acting mixed opioid agonist-antagonist with properties similar to either methadone or naltrexone, depending on dose. Clinical use, limitations, and outcome with each medication are reviewed.