The study's purpose is to examine the effectiveness of Motivational Enhancement Therapy (MET) on motivation to change as measured by the University of Rhode Island Change Assessment (URICA; McConnaughy, Prochaska & Velicer, 1983). Participants were drawn from a convenience sample of 22 adolescent males (treatment group n = 11; control group n = 11) who were in a mandated residential adolescent substance abuse program and who held a formal diagnosis of substance abuse or dependence. One-way repeated measures ANOVA (O'Rourke et al., 2005) utilized to examine the difference in the means of URICA among participants whose scores were recorded at three different times: before treatment, after treatment, and after a 5-weeks follow up. The overall results show that there is a statistical significance for the time effect. Additionally, there is a significant difference for the group time interaction effect, which indicates that the MET intervention is significant across time. Further, the simple main effects show no significant difference for the control group across times, but did find significant differences for the experimental group. Finally, tests on the group simple main effect indicated significant differences between control and experimental groups at the pre-assessment, but no significance difference were found between the control group and experimental group in either the post-assessment or follow-up assessments. Implications of the study and suggestions for future research are explored further. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]