Despite an abundance of research on interventions to improve social skills of young children with intellectual disabilities (ID), there is limited research on interventions aimed at improving social skills of adults with ID. The purpose of this single-subject study was to evaluate the outcomes of the Behavioral Opportunities for Social Skills (BOSS) teaching program for adults with ID. The theoretical framework for this study was Skinner's operant conditioning which incorporates the principles of applied behavior analysis, reinforcement, and operant extinction. After direct support professionals were trained in the BOSS teaching program, research questions were used to determine (a) changes in the frequency of praise statements given by direct support professionals to adults with ID; (b) differences in the frequency of cooperative and polite behaviors of adults with ID; and (c) increases or decreases in the frequency of challenging behaviors exhibited by adults with ID. A multiple-baseline design across participants and settings was used to evaluate the behavioral changes. Prosocial behaviors of 3 adults with ID and 3 direct support professionals' delivery of specific praise statements showed visually discernible increases and large effect sizes (ES [greater than or equal to] 0.92). The outcomes of this study contribute to positive social change as demonstrated by the positive behavioral changes achieved by the adults with ID who increased their prosocial behaviors and the direct support professionals who increased their delivery of specific praise statements following the implementation of the BOSS teaching program. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]