The appropriate therapeutic approach is considered in patients who present with carcinomatous metastases in the axillary lymph nodes and in whom the site of the primary tumor remains obscure. Eight patients with axillary lymph node metastases are reported, in 5 of whom the location of the primary tumor could not be established. In 3 patients the primary growth was ultimately found in the adjacent breast. Early death occurred in only 1 patient, and in this instance the primary site was in the breast. The remaining 7 patients showed a relatively good prognosis when compared with those in similar series reported in the literature. The conservative policy of using radiotherapy alone for such cases, and the more aggressive approach of blind radical mastectomy of the adjacent breast, are rejected. Instead, the more conservative sector mastectomy of the upper outer quadrant of the ipsilateral breast is proposed as a diagnostic procedure. Should this, together with general investigation of the patient, fail to detect the primary tumor, therapeutic axillary block disection followed by radiotherapy is advocated. If the primary tumor is found in the breast on sector mastectomy, a modified radical mastectomy of the affected breast should be performed and followed by irradiation.