ABSTRACT This article reviews research on the Transcendental Meditation (TM)1 program relevant to the treatment and prevention of criminal behavior and substance abuse. Over the past 30 years, 39 studies have been conducted on the rehabilitative effects of the TM program. These studies have involved various populations, including at-risk youth, participants in treatment programs, and incarcerated offenders. A few studies examined the effects of the TM program in the general population on use of alcohol, cigarettes, and non-prescribed drugs. Longitudinal, random-assignment studies with objective measures confirm the results of retrospective studies and other earlier research. Incarcerated offenders show rapid positive changes in risk factors associated with criminal behavior, including anxiety, aggression, hostility, moral judgment, in-prison rule infractions, and substance abuse.