In order to determine the long-term effects of an intensive treatment program, 17 adult and 25 adolescent stutterers were tested 2 or 3 times during a 12- to 24-month post-intensive treatment phase. The results of this study are intended to augment and supplement the growing body of evidence about the effects of intensive treatment programs on adult and adolescent stutterers. Follow-up measures included surprise phone calls to clients at home/work and a self-administered Speech Performance Questionnaire. Careful training of speech raters was undertaken to ensure high reliability of speech measures. Results from the phone call samples indicated that about 69% of the subjects maintained a satisfactory level of post-treatment fluency, with an additional 7% maintaining a level that was judged to be marginally satisfactory. On the self-administered Questionnaire, 80% of the subjects rated their speech fluency as good or fair 12 to 24 months after treatment.