This study examined fidelity in multidimensional family prevention (MDFP), a family-based prevention counseling model for adolescents at high risk for substance abuse and related behavior problems, in comparison to two empirically based treatments for adolescent drug abuse: multidimensional family therapy (MDFT) and cognitive-behavioral therapy (CBT). Randomly selected videotapes of 109 MDFP sessions, 57 MDFT sessions, and 31 CBT sessions were observationally rated along two key dimensions of implementation: intervention parameters and intervention techniques. Overall, MDFP was similar to MDFT and different from CBT in a manner congruent with its theoretical principles of interactional, systemic intervention. However, deficiencies in parental monitoring and developmental knowledge interventions point the way for continued model development. The utility of fidelity process research for conveying intervention technology along the prevention-treatment continuum of mental health services is discussed. © 2005 Wiley Periodicals, Inc. J Comm Psychol 33: 191–211, 2005.