The current system of care for treating individuals with substance use disorders evolved during the second half of the 20th century. It has roots in self-help movements and in medical and scientific research findings, and has been shaped by emerging drug trends, public health problems, and uneven treatment financing policies. Currently, the bulk of care is provided by: structured outpatient treatment programs; narcotic treatment programs; variable length residential programs (with and without medical services); and modified therapeutic communities. The majority of the services provided within these organizations meet professional credentialing and/or licensing requirements. The treatment delivery system has made great strides in the past decade to improve quality of care, incorporate outcomes monitoring, and increase the role of empirically supported treatments. Research on the effectiveness of substance abuse treatment indicates that the success rates for these services are comparable to other areas of medical/psychiatric care.