Treatment of patients with isolated axillary nodal metastases from an occult primary carcinoma consistent with breast origin. The records of 42 patients who had axillary metastases compatible with a clinically occult breast primary were reviewed. Forty patients had mammography performed as part of their evaluations. Mastectomy yielded the primary tumor in one of 13 patients; biopsy yielded positive results in one of five. Among the 29 patients who did not undergo mastectomy, 16 received breast irradiation, and 13 were simply observed for signs of the primary tumor. For the patients who did not undergo mastectomy, the 5-year actuarial risk for appearance of a primary was 17% in the irradiated group versus 57% in the nonirradiated group (P = 0.06). Patterns of failure are correlated with stage and local and systemic therapy. The results affirm our belief that patients with axillary metastases histologically consistent with breast tumor should be treated identically to patients with similar nodal stages and proven breast primaries. 