Factors which influence patient prognosis following a breast recurrence or regional nodal recurrence after initial treatment of early-stage invasive breast carcinoma with conservative surgery and radiotherapy are not well known. Ninety patients treated at the Joint Center for Radiation Therapy treated from 1968-1981 had a recurrence in the treated breast before (84) or simultaneous with (6) distant metastases. Sixty-five patients had salvage mastectomy (median subsequent follow-up in patients without further disease, 32 months; range, 1-123 months). The five-year rate of further recurrence in this group was 37%. The most important variable associated with subsequent outcome was the histology of the recurrent tumor. There were no further recurrences among 10 patients with purely non-invasive cancer or 10 patients with predominantly non-invasive disease and only focal areas of invasion. In contrast, 17/45 patients (38%) with predominantly infiltrating tumors suffered further local-regional recurrences (6) or distant metastases (11) following mastectomy (5-year actuarial rate, 55%) (p less than 0.05). Ten patients developed regional nodal failures without evidence of simultaneous breast recurrence (1 internal mammary, 3 supraclavicular, 1 both supraclavicular and axillary, and 5 axillary). Only 3 of these 10 (all with axillary node failures) did not have simultaneous distant metastases; they remain alive without evidence of further distant or local-regional recurrence following salvage treatment 1, 59, and 87 months after recurrence. We conclude that the great majority of the patients (88% in this series) who have a breast recurrence following initial conservative surgery and radiation therapy for early stage breast carcinoma will have disease limited to the breast clinically and tumors amenable to salvage mastectomy. Salvage mastectomy appears to be effective treatment for patients with an isolated breast recurrence, especially if the recurrence is predominantly or wholly non-invasive.