: Although treatment of co-occurring behavioral and physical health problems could be facilitated by the linkages between health care providers, it is uncertain how such inter-agency linkages are affected by managed care. We used a sample of 167 service linkages to examine the effects of managed care arrangements on inter-agency communication, coordination, and perceived effectiveness. These linkages were identified based on interviews with 62 outpatient substance abuse treatment units in 2000. Results indicate that frequency of communication and inter-agency coordination are positively related to several managed care arrangements and may moderate the relationships between managed care arrangements and perceived effectiveness.