Local-regional recurrence following mastectomy is not always a sign of poor prognosis. In an attempt to determine these subgroups of patients we analysed 149 patients of our radiation oncology clinic treated between 1978 and 1988 with local or regional recurrence (LR) following mastectomy. Average follow up was 66 months, 47% of these patients developed their recurrence in the first two years, 78% in five years, 90% of the local-regional recurrence appeared in the first ten years. Prognostic features which predicted a poor prognosis in combination with locoregional recurrence after mastectomy were identified; early local recurrence (less than two years from mastectomy) (p less than 0.001), large tumor size T3 and T4 primary) (p less than 0.001), less than five involved axillary lymph nodes (p less than 0.001), negative hormone receptor status, histological grading 3 and 4, lymphangiosis carcinomatosa in the tumor site (p less than 0.05), the presence of tumor-necrosis in the primary tumor (p less than 0.001) and appearance despite of postoperative irradiation (p less than 0.05). Prognosis of patients with more than five involved axillary lymph nodes did not change by local-regional recurrence. The local recurrence did not influence survival in: late local recurrence (more than two years from mastectomy), small tumor size (T1 and T2), negative axillary status, positive hormonal status, histologic grading 1 and 2 and absence of tumor-necrosis or lymphangiosis carcinomatosa in the primary tumor. We conclude that local-regional recurrence is in fact under the above defined circumstances not a sign of systemic disease. With insufficient local therapy it can under these conditions be cause of progressive tumor spread. Thus we strongly support intensive local therapy for local-regional recurrence.