To determine the prognostic significance of local relapse after conservative treatment of an invasive carcinoma of the breast, we analysed the results obtained in a series of 512 patients. All patients had a lumpectomy with axillary dissection followed by irradiation. Adjuvant medical treatment was administered to 168 patients. The actuarial 5 years and 10 years overall survival rates were respectively 92.5% and 79.7%. Local relapses occurred in 35 patients (6.8%). The actuarial 5 and 10 years local control rates were respectively 91.2% and 83.6%. In these patients, risk of metastasis was significantly increased as compared with patients without a local relapse. Recurrence in the breast within 2 years of initial treatment several affected the risk of metastasis occurring as compared to later relapses. We conclude that the occurrence of a breast relapse after successful local conservative treatment is a bad prognostic factor, predictive of a high risk for the development of distant metastases.