Purpose: The aim of the present study was to analyze deposits in bone marrow for determining micrometastases in breast cancer patients by flow cytometry. And its correlation of prognostic factors and macrometastasis at the first diagnosis. Material and Methods: Bone marrow samples were obtained from 52 breast cancer patients and 16 control patients via aspiration from the iliac spine at the time of first diagnosis after the surgery. Epithelial cells were identified with anticytokeratin monoclonal antibody, and double-staining with propidium iodide and CD45using flow cytometry. Results: In all, 2 (12.5%) of the 16 control patients and 11 (21%) of the 52 breast cancer patients had cytokeratin-18 positive cells in their bone marrow. A relationship between the presence of occult metastatic cells in bone marrow, and the presence/absence of lymph node metastases, tumor size, stage, menopausal status, hormone receptor status, histological grade, c-erb-B2 expression, tumor subtype, lymphovascular invasion, Ductal carcinoma in situ (DCIS) component, and gender was not observed. Significant positive relationships were observed between bone marrow micrometastasis, and age, and bone, bone marrow, lung, and liver metastases. Conclusion: Bone marrow micrometastasis was associated with age, bone, bone marrow, lung, and liver metastases at the time of diagnosis..