Cell-mediated immune (CMI) responses to tumor-associated antigens (TAA) in the early postoperative period were examined for correlations with disease recurrence and survival in a 13-year-prospective study of 77 stage 1 and 2 breast cancer patients treated with modified radical or radical mastectomy alone. Among the 21 patients who had positive lymphoproliferative tests using patients' peripheral blood mononuclear cells and autologous TAA of breast cancer cells, only one died from metastatic disease (5%). Among the 56 patients who had a negative test, 23 died from metastatic disease (41%). This difference is statistically significant (p = 0.002) Three other risk factors including tumor size, nodal status and cell differentiation patterns were also analyzed. When these three clinical-pathologic criteria were analyzed individually, none reliably predicted disease recurrence and survival. Nodal status was the most predictive clinical-pathologic risk factor, but was not significant (p = 0.089). The results of this study demonstrate the detection of CMI responses against autologous TAA by lymphoproliferative assays identifies a sub-set of stage 1 and 2 breast cancer patients who are at minimal risk of developing metastatic disease. This testing also identifies immunologically unreactive patients who are at risk for disease recurrence.