Heroin is a highly addictive drug and is the most widely abused and 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.

Pure heroin, which is a white powder with a bitter taste, is rarely sold on the streets. Most illicit heroin is a powder varying in color from white to dark brown. The differences in color are due to impurities left from the manufacturing process or the presence of additives. Another form of heroin, "black tar" heroin, is primarily available in the western and southwestern U.S. This heroin, which is produced in Mexico, may be sticky like roofing tar or hard like coal, with its color varying from dark brown to black.

Heroin can be injected, smoked, or sniffed/snorted. Injection is the most efficient way to administer low-purity heroin. The availability of high-purity heroin, however, and the fear of infection by sharing needles has made snorting and smoking the drug more common. National Institute on Drug Abuse (NIDA) researchers have confirmed that all forms of heroin administration are addictive.

According to the 2006 National Survey on Drug Use and Health (NSDUH), approximately 3.8 million Americans aged 12 or older reported trying heroin at least once during their lifetimes, representing 1.5% of the population aged 12 or older. Approximately 560,000 (0.2%) reported past year heroin use and 338,000 (0.1%) reported past month heroin use.

The 2006 NSDUH results also indicate that there were 91,000 persons aged 12 or older who had used heroin for the first time within the past 12 months. The average age at first use among recent initiates aged 12 to 49 was 20.7 years in 2006. There were no significant changes in the number of initiates or in the average age at first use from 2005 to 2006.

Among students surveyed as part of the 2007 Monitoring the Future study, 1.3% of eighth graders and 1.5% of tenth and twelfth graders reported lifetime use of heroin.

A variety of effective treatments are available for heroin addiction. For example, methadone, a synthetic opiate that blocks the effects of heroin and eliminates withdrawal symptoms, has proven successful for heroin addiction. Additionally, buprenorphine and many behavioral therapies are also used to treat heroin addiction.

From 1996 to 2006, the number of admissions to treatment in which heroin was the primary drug of abuse increased from 224,366 in 1996 to 245,984 in 2006. Heroin admissions represented 13.6% of the total drug/alcohol admissions to treatment during 1996 and 13.7% of the treatment admissions in 2006. The average age of those admitted to treatment for heroin during 2006 was 36 years. Those admitted to treatment for heroin during 2006 were primarily male (68%) and white (52%).