The NHSDA yields prevalence estimates on: alcohol, tobacco, cannabis, cocaine, inhalants, hallucinogens, heroin, and the non-medical use of psychotherapeutic agents. The survey includes the US population aged 12 and over and derives its estimates from a national probability sample of households throughout the country. The study indicates that overall rates of illicit drug use peaked in the US around 1979, and have since been decreasing. The MTF study, a nationally representative survey of high school seniors and young adults, shows a peaking in rates of drug use about the same time. The article discusses limitations of general population studies, the Drug Abuse Warning Network, Drug Abuse and Criminality, the Drug Use Forecasting study, the Office of National Drug Control Policy, and the DC Metropolitan Area Opinion Leaders' Study. There are limited data available to respond to several of the premises on which current drug policy is based, but they suggest that drug policy is not having the desired effect: (1) Availability and prices appear to have been largely unchanged; (2) The biggest declines in drug use have been among casual users, those least likely to show up in jails or emergency rooms; (3) While there has been a considerable reduction in the prevalence of illicit drug use for society as a whole, the numbers of cocaine-related emergency room visits and deaths have been increasing since at least the late 1970s; and (4) Heroin-related emergency room episodes increased fivefold between 1978 and 1993. Table, figures, references