Aim of this study was to evaluate the feasibility, therapeutic effectiveness and toxicity of a non conventional radiation therapy (180 cGy twice a day for a total dose of 36 Gy in 2 weeks in the treatment of breast cancer inoperable with conservative surgery as first choice. Ten patients were studied. Results were as follows: complete response: 20%, partial response: 70%; no change: 10%. Acute toxicity was negligible and late toxicity, after a mean 46-month follow-up, was practically absent; the cosmetic result was definitely good. The radiobiology and kinetic features of breast cancer indicate that the potential of accelerated treatment should be further explored, this fractionation being suitable for optimal combined modality treatment with preoperative chemotherapy.