Purpose: to compare the surgery and radiotherapy related outcomes, toxicities and cosmesis of patients undergoing breast conserving surgery and adjuvant external beam radiotherapy having intraoperative electron boost radiotherapy (IEBR) versus postoperative interstitinal brachytherapy (PIB).Materials and methods: Between January 2007 and October 2009, 200 women with a diagnosis of early breast cancer were treated with lumpectomy, sentinel node biopsy,with or without axillary lymphadenectomy.During surgery an electron boost of 9 Gy (4-12 Mev) was administered to the tumor bed using a Mobetron (Intraop, USA).Adjuvant treatment was completed with whole breast external beam radiotherapy (WBEBR, 45 Gy in 25 fractions) and systemic therapy if necessary (group 1).The outcomes in these patients was compared propectively to 100 stage-matched patients treated in the same period having similar breast conserving surgery, systemic treatment and WBEBR, and receiving a boost by means of postoperative interstitional brachytherapy (192Iridium, 15 Gy, Nucletron Afterloader, USA) implanted under general anesthesia according to the Paris system (group 2).Results: Median netto (=incision to closure) and bruto (=total time spend in the operating theatre) time in the operating theatre at primary surgery was significantly higher in group 1 (respectively 99 vs 62 min, p<0.01, and 118 and 80 min, p<0.01).Netto and bruto time to implant the iridium wires respectively was 27 and 50 min.This means that the total theatre time was comparable in both groups (netto 96 vs 89 minutes, and bruto 148 vs 130 minutes, NS).Perioperative morbidity was slightly higher in group 1 due to a higher amount of postoperative wound infections (15/200 vs 4/100, p<0.05).Median total surgery and radiotherapy related hospital stay for the entire treatment was 2.5 days in group 1 and 4.0 days in group 2 (p<0.01).Patient satisfaction was significantly higher in patients receiving IEBR.Acute skin toxicity at the end of the entire treatment was significantly lower in group 1.Out of 134 evaluable patients after 6 months there were no patients with grade 4 skin toxicity in group 1.No tumor recurrences were seen in both groups after a median follow-up 10 months.Conclusions: Intraoperative radiotherapy is feasible and well tolerated in selected patients with early breast cancer.Total hospital stay is lower and patient satisfaction is higher in women having IEBR compared to PIB.Our study suggests it may be considered to give patients undergoing IEBR prophylactic antibiotic treatment.