Investigated with a 26-year-old male graduate student were the immediate and long-term effects of social reinforcement and feedback on the incidence of stuttering. The S's speech dysfluencies were recorded under baseline and intervention conditions in three settings: two classes the S taught and a weekly hour-long conversation period with peers. Reinforcement consisted of graphic feedback (histograms) of the percent decrease in disfluency (delivered immediately after each session) and verbal praise. Intervention was judged successful due to the 62 percent decrease in stuttering at the end of intervention, and a 95 percent decrease observed at the 3-month maintenance check. (LS)