The advantages of breast reconstruction using the deep inferior epigastric perforator (DIEP) flap and the muscle-sparing free transverse rectus abdominis musculocutaneous (TRAM) flap (MS-2) are well recognized. Both techniques optimize abdominal function by maintaining the vascularity, innervation, and continuity of the rectus abdominis muscle. The purpose of this study was to compare these two methods of breast reconstruction and determine whether there is a difference in outcome. The study considered 177 women who have had breast reconstruction using muscle-sparing flaps over a 4-year period. This includes 89 women who had an MS-2 free TRAM flap procedure, of which 65 were unilateral and 24 were bilateral, and 88 women who had a DIEP flap procedure, of which 66 were unilateral and 22 were bilateral. The total number of flaps was 223. Mean follow-up was 23 months (range, 3 to 49 months). For all MS-2 free TRAM flaps (n = 113), outcome included fat necrosis in eight (7.1 percent), venous congestion in three (2.7 percent), and total necrosis in two (1.8 percent). For the women who had an MS-2 free TRAM flap, an abdominal bulge occurred in three women (4.6 percent) after unilateral reconstruction and in five women (21 percent) after bilateral reconstruction. The ability to perform sit-ups was noted in 63 women (97 percent) after unilateral reconstruction and 20 women (83 percent) after bilateral reconstruction. For all DIEP flaps (n = 110), outcome included fat necrosis in seven (6.4 percent), venous congestion in five (4.5 percent), and total necrosis in three (2.7 percent) patients. For the women who had DIEP flap reconstruction, an abdominal bulge occurred in one woman (1.5 percent) after unilateral reconstruction and in one woman (4.5 percent) after bilateral reconstruction. The ability to perform sit-ups was noted in all women after unilateral reconstruction and in 21 women (95 percent) after bilateral reconstruction. These results demonstrate that there are no significant differences in fat necrosis, venous congestion, or flap necrosis after DIEP or MS-2 free TRAM flap reconstruction. The percentage of women who are able to perform sit-ups and the percentage of women who did not develop a postoperative abdominal bulge is increased after DIEP flap reconstruction; however, this difference is not statistically significant.