The resource cost (cost to our hospital) of providing mastectomy plus breast reconstruction was calculated for 276 patients who had received both mastectomy and breast reconstruction at our institution. All patients had completed the entire reconstructive process, including reconstruction of the nipple. The resource costs of providing mastectomy with immediate breast reconstruction were compared with those of mastectomy with subsequent delayed reconstruction. We found that the mean resource cost for the 57 patients who had separate mastectomy followed by delayed breast reconstruction ($28,843) was 62 percent higher than that of mastectomy with immediate reconstruction($17,801; n = 219, p < 0.001). Similar differences were found when patients were subgrouped by type of reconstruction (TRAM versus tissue expansion and implants), by laterality (unilateral versus bilateral), and by history of preoperative irradiation. We conclude that mastectomy with immediate breast reconstruction is significantly less expensive than mastectomy followed by delayed reconstruction and can potentially conserve resources.