This case study examines a 13 year old adolescent male who engages in severe aggression, self- injurious and impulsive behaviors. He was treated with Dialectical Behavior Therapy (DBT) for thirteen months. DBT had limited success in reducing his problem behaviors. He was treated with Mode Deactivation Therapy (MDT) for four months and his problem behaviors were reduced significantly. It appears that in this case study MDT was more effective than DBT in reducing his severe behaviors. (Contains 4 tables.)