The four drug abuse programs selected were two from the U.S. -- the U.S. Army program, and the program of the Washington, D.C. metropolitan area and two outside the U.S. -- in England and Japan. The U.S. Army program to control heroin addiction among troops serving in Vietnam has incorporated epidemiological principles: mandatory urine testing and treatment of all active cases. The Washington, D.C. program uses an epidemiological surveillance system -- questionnaire and urine testing -- to analyze the associations between metropolitan crime trends, drug arrest and seizure statistics, treatment program admission data, and deaths due to drug overdosage. The drug treatment system in England has a distinctly medical rather than punitive orientation; treatment is available to all who seek it. The Japanese approach relies on control of the drug supply and a vigorous effort to identify all active cases and involve them in treatment. All these programs place major emphasis upon intensive case-finding efforts to identify and treat all active addicts and the monitoring of incidence, prevalence, and other epidemiological trends to evaluate the impact of treatment and other control measures over time.