Abstract The adaptation effect in stuttering behavior has received considerable attention. Adaptation effect is defined as the reduction in the frequency of nonfluencies in the speech of subjects during successive readings of the same passage. The objective of this investigation was to assess the adaptation effect of nonfluent speech behavior of controlled stutterers and nonstutterers. The subjects included 35 controlled stutterers and 35 nonstutterers matched for factors of sex, grade level, and age. Results suggest a significant mean difference between the number of nonfluencies between trials of controlled stutterers with evidence of adaptation in the speech of nonstutterers. Nonstutterers demonstrate significant mean differences in nonfluencies among replicated testing occasions. Findings of this investigation suggest that both controlled stutterers and nonstutterers demonstrate similar adaptation regarding their nonfluent speech behavior. Issues and import for future research are offered.