Teacher-Child Interaction Therapy (TCIT), which is an adaptation of the empirically-based treatment of Parent-Child Interaction Therapy (PCIT), addresses the needs of children and teachers through increasing positive teacher-child interactions while educating teachers on effective discipline techniques. The theoretical and empirical basis for PCIT provides the foundation for the appropriate and effective application of the adaptation of this treatment model for use with teachers. The efficacy of Teacher-Child Interaction Therapy (TCIT) with a clinical preschool population was evaluated through a single subject A-B design conducted across subjects. The current study examined the impact of the intervention, TCIT, on child behavior, teacher skill development and use, as well as the quality of teacher-child relationships. Results suggest that the intervention positively impacted the behavior of preschool children diagnosed with a Disruptive Behavior Disorder, as indicated by a reduction of disruptive behaviors and increase of prosocial behaviors within a therapeutic classroom setting. Additionally, teacher skill use and the quality of teacher-child relationships were evaluated following implementation of the TCIT intervention. Findings indicate that the intervention positively impacted teachers' use of the positive attention skills over the course of the intervention. This study, which examined the efficacy of Teacher-Child Interaction Therapy with preschool-aged children diagnosed with a Disruptive Behavior Disorder, provides initial support for the implementation of a relationship-based technique to support teachers in addressing the disruptive behaviors of children within a classroom environment. [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/en-US/products/dissertations/individuals.shtml.]