Against a backdrop of increasing concern about the adequacy of treatment for co-occurring substance use and mental disorders (typically known as “co-occurring disorders,” or COD) in the criminal justice system, this article attempts to provide empirical evidence for a typology of levels of COD treatment for offenders in both prison and community settings. The paper investigates two levels of treatment programs for COD; “intermediate” programs, in which treatment programming has been designed primarily for offenders with a single disorder, and “advanced” programs, in which programming has been designed to provide integrated substance abuse treatment and mental health services. Findings from a national survey of program directors indicated that both intermediate and advanced COD treatment programs were similar in their general approach to substance abuse treatment, but differed considerably in their treatment of mental disorders, where the advanced programs employed significantly more evidence- and consensus-based practices. Results provide support for the distinction between intermediate- and advanced-level services for offenders with COD and support a typology that defines advanced programs as integrating a range of evidence- and consensus-based practices so as to modify treatment sufficiently to address both diseases. Copyright © 2008 John Wiley & Sons, Ltd.