Heroin is an illegal, highly addictive drug. It is both the most abused and the most rapidly acting of the opiates. Heroin is processed from morphine, a naturally occurring substance extracted from the seed pod of certain varieties of poppy plants. It is typically sold as a white or brownish powder or as the black sticky substance known on the streets as "black tar heroin." Although purer heroin is becoming more common, most street heroin is "cut" with other drugs or with substances such as sugar, starch, powdered milk, or quinine. Street heroin also can be cut with strychnine or other poisons. Because heroin abusers do not know the actual strength of the drug or its true contents, they are at risk of overdose or death. Heroin also poses special problems because of the transmission of HIV and other diseases that can occur from sharing needles or other injection equipment.

According to the 2003 National Survey on Drug Use and Health, which may actually underestimate illicit opiate (heroin) use, an estimated 3.7 million people had used heroin at some time in their lives, and over 119,000 of them reported using it within the month preceding the survey. An estimated 314,000 Americans used heroin in the past year, and the group that represented the highest number of those users were 26 or older. The survey reported that, from 1995 through 2002, the annual number of new heroin users ranged from 121,000 to 164,000. During this period, most new users were age 18 or older (on average, 75 percent) and most were male. In 2003, 57.4 percent of past year heroin users were classified with dependence on or abuse of heroin, and an estimated 281,000 persons received treatment for heroin abuse.

According to the Monitoring the Future survey, NIDA's nationwide annual survey of drug use among the Nation's 8th-, 10th-, and 12th-graders, heroin use remained stable from 2003 to 2004. Lifetime heroin use measured 1.6 percent among 8th-graders and 1.5 percent among 10th- and 12th-graders.

The 2002 Drug Abuse Warning Network (DAWN), which collects data on drug-related hospital emergency department (ED) episodes from 21 metropolitan areas, reported that in 2002, heroin-related ED episodes numbered 93,519.

NIDA's Community Epidemiology Work Group (CEWG), which provides information about the nature and patterns of drug use in 21 areas, reported in its December 2003 publication that heroin was mentioned as the primary drug of abuse for large portions of drug abuse treatment admissions in Baltimore, Boston, Detroit, Los Angeles, Newark, New York, and San Francisco.

Heroin is usually injected, sniffed/snorted, or smoked. Typically, a heroin abuser may inject up to four times a day. Intravenous injection provides the greatest intensity and most rapid onset of euphoria (7 to 8 seconds), while intramuscular injection produces a relatively slow onset of euphoria (5 to 8 minutes). When heroin is sniffed or smoked, peak effects are usually felt within 10 to 15 minutes. NIDA researchers have confirmed that all forms of heroin administration are addictive.