The objective was to elaborate a method of immunohistochemical diagnosis of bone micrometastases and to apply this procedure in operated patients with the non-small cell form of lung cancer. By means of a cocktail of cytokeratin mixtures and individual cytokeratins the immunohistochemical profile of the primary pulmonary focus is assessed. Bone micrometastases are evaluated from the bone marrow of a sampled costal segment. A total of 30 bone marrow samples were examined. For further evaluation 17 patients remained in the group. Isolated segments with a marked positivity of cytokeratins were observed in four instances. The yield of bone marrow from costal segment is very good. The initial results are encouraging for further research.