Detection of cytokeratin-positive cells in bone marrow and peripheral blood may have prognostic significance in cancer patients. Furthermore, a correlation between uPAR expression on micrometastases and patient prognosis has been suggested. However, in patients with colorectal cancer, preoperative detection and characterization of tumour cells in bone marrow and peripheral blood, using an immunocytochemical approach, have not yet been substantiated as a prognostic tool. METHODS: Forty-one bone marrow aspirates and 38 peripheral blood aspirates, obtained preoperatively from patients with colorectal cancer, were immunocytochemically screened for cytokeratin-positive cells. Where cytokeratin-positive cells were observed, an additional microslide was double immunostained for simultaneous detection of cytokeratin and uPAR/CD87. RESULTS: Cytokeratin-positive cells were observed in 4 out of 41 bone marrow aspirates (10%). None of the isolated cytokeratin-positive cells expressed uPAR. In peripheral blood, no cytokeratin-positive cells were observed. CONCLUSION: The present study does not support the introduction of a routine immunocytochemical identification of cytokeratin-positive cells in preoperatively obtained bone marrow aspirates or peripheral blood from patients with colorectal cancer.