Epidemiology is described for depressants, stimulants, hallucinogens, solvents and inhalants, and marijuana. Theories of addiction and dependence pertain to social psychological typology, life-cycle theory, psychoanalytic theory, psychiatric theory, and learning theory. After discussing the opioid sales and use patterns in America, the chapter addresses drug laws and enforcement patterns. Treatment strategies described include the use of coercion by criminal justice agencies, therapeutic communities, and methadone maintenance. The identified social costs of drug dependence include expenses for law enforcement, courts, prisons, treatment, crime, property losses, illnesses, shortened life span, and taxes not paid because of unemployment and loss of life. The discussion of policy development focuses on the Federal Government's strategy of limiting the drug supply, discouraging use by prevention, and treatment. The future depends on whether policymakers recognize that efforts to reduce drug supplies will be futile without a strong effort to reduce demand. 72 references.