In one of the few studies of the performance of children under social-comparison feedback (information about other's performance relative to one's o w n ) , McClintock and Van Avermaet (1975) showed that feedback produces higher performance than no feedback. Their manipulation, however, was limited to three 4-min. trials. The first goal of the present study was to examine the effecc of social-comparison feedback .upon children's performance over a considerable period of time ( 5 6 trials). The second goal was to examine the effect of advance instruction that feedback would or would not be glven. Four pairs of boys, 10 to 11 years of age, performed a button-pushing task that required discriminations between different-colored lights. There were four periods in the experiment: Baseline 1 ( 5 days), with no feedback given; Feedback plus N o Feedback ( 1 3 days), consisting of two trials with and one trial without feedback; Baseline 2 ( 9 days). again, with no feedback; and Feedback Only ( 1 0 days), for three trials with feedback per day. Presentation order of Feedback plus N o Feedback and of Feedback Only mas counterbalanced. During these two feedback periods the experimenter placed white pegs (child's own score) and red pegs (partner's score) in appropriate places on each child's feedback board immediately after each feedback trial. Median scores were computed to summarize performance under each of the four periods. An analysis of variance of these scores indicated that response rate was higher under the feedback periods (Feedback plus N o Feedback and Feedback Only) than under the baeline periods ( K . 6 = 54.38, p < ,001). Furthermore, response rate was higher under the second two periods (Baseline 2 and the counterbalanced feedback period) than under the preceding two periods ( K , a = 18.11, p < .002). Over-all social-comparison feedback increased response rate and maintained it over an extended period. The effect of advance instructions about whether feedback would occur was examined by focusing on the changes in scores on individual trials in the Feedback plus N o Feedback period. When no feedback was given on the first trial and the instructions indicated that feedback would be given on the second trial, the mean proportion of trial sequences in which the child increased his response rate was 96.7, matched-pairs t with control = 4.53, p < .005. When feedback had been given for the first trial, and the instructions indicated that no feedback would be given for the second trial, the mean proportion of trial sequences in which the child decreased his response rate was 90, t for comparison with control = 6.29, p < .001. Thus, the effect of instruction on responding was immediate. This effect seemed to be independent of possible effects due to feedback given for the previous trial.