For women undergoing breast-conserving surgery, recent reports suggest that in selected cases accelerated partial breast irradiation may yield results equal to that of whole breast irradiation. Over 31 months, 19 patients underwent accelerated partial breast irradiation using the MammoSite as the sole radiation treatment following breast-conserving surgery. Seventeen patients had the MammoSite inserted postoperatively using the scar entry technique (SET). Treatments were delivered using high dose rate iridium 192 given twice a day for 5 days. Three complications (two minor, one major) occurred. Late radiation morbidity and overall cosmetic results were evaluated. Eighty percent of patients had either no change from baseline or slight change in skin pigment. More than 90% had good or excellent overall cosmetic outcomes. Patients undergoing accelerated partial breast irradiation with the MammoSite inserted using SET had excellent overall cosmetic results. Advantages of the SET over intraoperative placement are presented.