In an effort to achieve external stimulus control within a response-correlated chain, 32 albino rats were given an intertrial interval procedure which reversed the correlation between rate of responding and within-chain delay of reinforcement which obtained during the approach trial. With this procedure, unlike previous findings with response-correlated chains, bar-pressing rate varied with the similarity of external stimulation to stimulation present during reinforcement (discriminative stimulus control) and with the intensity of external stimulation (stimulus intensity control of dynamism). The results are consistent with the hypothesis that internal stimulation controls performance within response-correlated chains because of the differential reinforcement of response-produced stimuli which change progressively as a function of continued responding. These findings, together with earlier research, place severe limitations on the extent to which external stimuli may carry the explanatory burden in theoretical analyses of response-correlated approach chains. (PsycINFO Database Record (c) 2006 APA, all rights reserved)