An analysis of recent national studies on drug treatment services for prison inmates showed that out of the 500,000 inmates with substance abuse problems, State prisons can provide drug treatment to just over 100,000. The more intensive treatment was provided to those inmates nearing release. In the five States visited, the prison drug treatment services were either in the process of being expanded or improved. The Services ranged from drug education, self-help, and professional counseling programs to more intensive residential treatment programs and after care programs. Challenges to drug treatment services include limited funding, security considerations, and difficulties in assuring the availability of after care. Federal government information and assistance is needed to implement effective prison treatment programs.