This seminar paper reports case studies in the successful use of adult social reinforcement to modify problem behaviors of individual children in the Laboratory Preschool at the University of Washington, Seattle. After initially determining that teacher behavior functioned as a reinforcer in accordance with reinforcement principles, it became possible to study the effects of adult attention on behavior deficits such as excessive crying, extreme passivity, excessive isolate behavior, lack of speech, and hyperactivity. Through text and tables, a brief description of the reinforcement program for each of nine "problem" children is presented. Collectively, the case studies demonstrate the effectiveness of adult social reinforcement as a tool for helping children modify behaviors that handicap them. WY)