Fifty patients who underwent unilateral breast reconstruction by transverse rectus abdominis musculocutaneous flap transposition between January 1987 and December 1989 are the object of this study. Every patient underwent selective harvesting of the medial portion of the muscle, whereas the lateral strip was left in place and studied intraoperatively by selective stimulation of the ninth intercostal motor nerve before closure of the fascial defect. Two separate ecographic scans of the abdominal wall were performed respectively 7 days and 6 months postoperatively, to evaluate the diameters of the residual portion of the rectus muscle and its long-term evolution. Our results show that in a considerable number of patients, the lateral strip of rectus was denervated at surgery. Long-term ecographic scans demonstrate, however, that in spite of this finding, the residual muscle usually maintains its diameters, thus significantly contributing to the competence of the abdominal wall, at least from the static point of view.