Flow cytometric DNA analysis has been applied as an important factor for decision of postoperative therapeutic regimen and prediction of prognosis of breast cancer. Sinus histiocytosis had been recognized as a better prognosic factor in axillary lymph nodes than negative sinus histiocytosis. It represents not only the presence of metastases, but also their immunologic potential and cell mediated immunity against the tumor. This study examined DNA ploidy pattern, S-phase fraction and sinus histiocytosis in axillary lymph nodes of breast cancer in 131 patients who underwent operation at the Department of Surgery, Hanyang University Hospital during the period of January 1990 through February 1993. On the basis of these datas, we analysed the correlation of tumor DNA ploidy and axillary lymph node changes with other prognostic factors which are TNM status, histologic grade and estrogen receptor in breast cancer. Authors obtained the following results; 1) In 131 patients, aneuploidy was 63(48.1%) and high S-phase fraction was 89(68%) 2) Incidence of aneuploidy and high S-phase fraction was increased according to the aggravation of T factor, N factor and poor histiologic grade. The rate of negative estrogen receptor was high in aneuploidy and high S-phase fraction group. 3) Among 102 patients, 53(50.1%) had positive sinus histiocytosis, 49(49.9%) had negative sinus histiocytosis. The positive rate of sinus histiocytosis in axillary lymph nodes was highly related with negative axillary lymph node metastases and small size of tumor and it was lower in aneuploidy and high S-phase fraction. 4) Among the patients as a whole postoperative early recurrence were present in 8 cases, they had poor TNM staging and high correlation to aneuploidy, high S-phase fraction and sinus histiocytosis seem to be useful prognostic factors. And additional follow up studies for survival is required.