Summary: Although the prevalence of illicit drug use in the past year has declined overall since the 1980s--when crack cocaine use in the United States was reported to have reached epidemic proportions--drug use remains a serious national public health problem. In 1996, an estimated 13 million Americans aged 12 and older had used an illicit drug in the past month. Moreover, national survey data indicate that the recent downward trend in illicit drug use among youth has reversed. The costs of drug abuse to society--from drug treatment to lost earnings--were pegged at about $110 billion in 1995. Each year since the mid-1980s, Congress has set aside billions of dollars for federal agencies to reduce the supply of and demand for illegal drugs. In light of continuing concerns about the demand for drugs and emerging drug use problems, this report examines the efforts of federal public health agencies to detect the spread of drug use in the United States and their ability to respond to potential drug crises. This report (1) describes how public health service agencies have detected and responded to the crack cocaine epidemic, (2) identifies any changes made to improve the United State's drug detection and response capability, and (3) identifies any remaining issues that could compromise the nation's ability to detect and respond to emerging drug problems.