Between 1970 and 1981, 436 patients with T1 and small T2 breast carcinoma were treated by tumor excision followed by radiotherapy at the Institut Gustave-Roussy. The mean follow-up was 5 years, with 50% of patients followed 5 years. Twenty-four patients have experienced a local-regional (LR) relapse for an actuarial LR control rate of 93% at 5 years and 90% at 10 years. Potential prognostic factors for all 24 local-regional recurrences and for the subgroup with relapses in the breast were analyzed. A high Bloom grade and low Nominal Standard Dose (NSD) were significant prognostic factors for predicting LR relapse in both groups. Disease-free survival (from initial presentation) was not adversely affected by a solitary breast recurrence, when patients with successful salvage treatment were considered disease free. However, the group of patients with nodal or dermal recurrences had a much worse prognosis. This paper describes the natural history of breast cancer following a local-regional relapse in irradiated patients without mastectomy. Most importantly, we observed that breast relapses following radiotherapy become clinically apparent more slowly than chest wall failures after mastectomy, and if detected early, that these patients may be successfully retreated.