The frequency, time course, and prognosis of local recurrence following primary radiation therapy in 152 patients with early breast cancer treated before 1967 were examined. Local recurrence occurred at a constant rate over the first 14 years after treatment. The crude 15-year local recurrence rate was 22%. Of the 30 patients who developed an isolated local recurrence and underwent definitive secondary surgery, the 10-year freedom from distant relapse rate was 50%. These results indicate that breast cancer patients treated by primary radiation therapy require long-term follow-up to detect curable local recurrences.