Two expts. were performed to investigate the role of reinforcement in verbal behavior. In Expt. I two groups of 20 adult male Ss responded to a series of 80 cards containing a verb and 6 personal pronounds. The Ss formed sentences containing the verb and beginning with any one of the pronouns. For Group I all sentences beginning with I or We were reinforced by E''s saying "Good"; Group II received no reinforcement. The results, arranged in 4 trials of 20 cards each, indicated successive increments in the reinforced response for Group I and no change for Group n. Expt. II concerned extinction following acquisition, and used 160 cards. The procedure governing acquisition was similar to Expt. I for three groups of 25 Ss. During extinction (the last 80 cards), reinforcement of I and We responses was discontinued for Group I and II. For Group n, however, reinforcement was shifted to He and They responses. Group III continued to receive reinforcement for I and We. Analysis indicated no significant decrease in I and We responses for Groups I and III. Group II, however, showed marked extinction of I and We and a concomitant increase in the use of He and They. Questioning of Ss typically revealed no awareness of the contingency between their responses and those of E.