This is a retrospective review of 556 patients who had carcinoma of the breast (1971-1980). Among the 476 patients who had mastectomy, 38% have died and the median follow-up time of those who were alive was 53 months. When the axillary nodes were free of metastasis initially, 18% of the patients had relapse. Among the patients who had axillary nodal metastasis, 24% of those with 1-3 positive nodes, and 69% of those with greater than or equal to 4 positive nodes relapsed. Regarding specific type of first recurrence, about 10-30% had loco-regional relapse, 60-70% had distant metastasis and 10-30% had both (patients with greater than or equal to 4 lymph nodes involved are less likely to have only loco-regional relapse). Postoperative radiotherapy decreased the frequency of isolated loco-regional relapse, but did not decrease the overall failure rate nor influence the chance of dissemination. Among patients who had one or more positive axillary nodes, adjuvant chemotherapy (melphalan or CMF) did not significantly decrease relapse rates nor change types of relapse. Thus, distant dissemination is the major problem for those who developed recurrence after mastectomy. The relative distribution of the initial spread is similar to that seen among the 80 patients who had Stage IV disease at diagnosis. The most common five sites are bone (which accounted for 40-60% of the distant metastasis), lung (15-22%), pleura (10-14%), soft tissue (7-15%), and liver (5-15%).