Between 1990 and 1999, the number of adults in State and Federal prisons and jails grew by almost 65 percent. Most of this growth was due to violent offenses, but arrests and convictions for drug law violations, even minor ones, were up significantly. A substantial majority of the 1.9 million who are now in prison or jail have used illegal drugs. Many have problems with alcohol and multiple drugs. Substance abuse treatment can help prevent disease and reduce crime. This can benefit inmates, their families, and the community. The criminal justice system offers a variety of interventions for drug users in prisons and jails, which include: detoxification, education and counseling, self-help groups, therapeutic communities (TC), methadone maintenance, diversion programs, including drug courts, intermediate sanctions, and coerced abstinence. But substance abuse treatment faces many challenges. One problem is that far fewer inmates receive treatment than could benefit from it. In addition, the programs that do exist vary in quality and content. Another problem is that the security concerns of the prison may conflict with some aspects of the substance abuse treatment, such as the need for prisoners to be moved from one part of a facility to another to participate in a substance abuse treatment. It is also the case that few prisons and jail systems focus adequately on life after prison. Essential support services after release include substance abuse treatment and employment, housing, education, primary health care, and mental health services. Various agencies, organizations and providers are working to establish and maintain innovative programs for drug users involved in the criminal justice system. These programs include: the National Compendium of Local and State Interventions for Substance-Abusing Persons Involved with the Justice System; the Residential Substance Abuse Treatment for State Prisoners Formula Grant Program (RSAT); Breaking the Cycle; and Treatment Accountability for Safer Communities (TSAC).