Specific allelic losses in the DNA of tumor cells are potential indicators of postoperative prognosis. Patients whose tumors showed allelic losses at 1p34, 3p25, 8p22, 13q12, 17p13.3, or 17q21.1 had a significantly higher risk of postoperative mortality than women whose tumors retained both alleles at those loci (the 5-year mortality rates in patients with loss vs those with retention were: at 1p34, 23% vs 10%, P = 0.0100; at 3p25, 22% vs 9%, P = 0.0014; at 8p22, 24% vs 7%, P = 0.0177; at 13q12, 19% vs 8%, P = 0.0093; at 17p13.3, 19% vs 9%, P = 0.0078; and at 17q21.1, 17% vs 10%, P = 0.0475). Allelic losses at these loci may serve as negative prognostic indicators to guide postoperative management, especially in the selection of patients who should be offered intensive adjuvant therapy.