Ten consecutive patients at Howard University Hospital underwent modified radical mastectomy with immediate breast reconstruction using a temporary tissue expander. Postoperative irradiation was delivered to the breast mound encompassing the tissue expander. The effects of expansion on the delivery of postoperative irradiation was assessed. Dosimetric measurements with thermoluminescent dosimeters revealed that the saline-filled expander attenuated the photon beam 3% less than tissue-equivalent material of equal volume. This dose variation was negligible, so no adjustments were made. Postoperative treatment consisted of 5040 cGy to 5220 cGy delivered in 5 to 10 weeks using 4 mV photon tangentials. Cosmesis was assessed over a 2-year period. Six patients completed reconstruction and irradiation without complications. Cosmesis was good in five and fair in one. One patient developed a moist reaction secondary to postoperative irradiation; however, final cosmesis was good. Three patients developed complications leading to the loss of the reconstructed breast. Successful final reconstruction can be achieved with careful patient selection and close follow-up by the plastic surgeon and radiation oncologist.