An earlier study in this laboratory found that preoperative overtraining improved retention of a delayed alternation task after prefrontal lesions in the rat. In this study, however, it was found that preoperative overtraining did not improve performance of the rat in a delayed response task following prefrontal lesions. These results support the hypothesis that preoperative overtraining can improve postoperative performance only when postoperative recovery is ordinarily present, as it is with delayed alternation, but not with delayed response, in the prefrontal rat. This suggests that effects of preoperative overtraining and postoperative recovery may be mediated by similar mechanisms. It further suggests that a shift of function, which seems to account for postoperative recovery, may occur in some parts of the normal adult brain as a result of overtraining.