Of 178 local recurrences occurring in 1593 patients with clinical Stages I-II breast cancer treated by conservative surgery and megavoltage radiotherapy, 71 were diagnosed after the 5th year. Compared with recurrences occurring prior to 60 months, late recurrences were less frequently inoperable (1/71, 1.4%, versus 18/107, 17%, p less than 0.001), were more often located at a distance from the initial primary tumor (23/71, 32%, versus 15/106, 14%, p less than 0.005), and had a more favorable prognosis (5-year survival 84% versus 61% for late and early operable recurrences, respectively, p = 0.05). Five-year metastasis-free survival after late failure depended mainly on the anatomic extent of the recurrence (87% for recurrences apparently confined to the breast versus 34% for relapses involving the axilla, p less than 0.002). Prognosis of late recurrence appeared to be unaffected both by location of the recurrence within the breast and by the type of salvage operation used (mastectomy versus wide excision). Local-regional control after salvage surgery was satisfactory (89% at 5 years). Whereas recurrence in the breast prior to 5 years profoundly affected survival after initial diagnosis, patients with late failure had identical 15-year survival as other 5-year survivors who never failed locally. Late recurrences were more frequent in patients younger than 40 at initial treatment, and in patients who had inadequate radiotherapy. We conclude that late local recurrences after breast conservation do not represent a serious management problem.