This study examined the clinicopathological significance of minichromosome maintenance-2 (MCM2) expression in 38 human malignant fibrous histiocytomas (MFHs) and 36 benign fibrohistiocytic tumors (BFHTs) immunohistochemically, and in 9 human sarcoma or carcinoma cell lines, as well as 7 surgical specimens by Western blotting. MCM2 was detected in all the cell lines and surgical specimens as a single band at 120 kDa, while P53 expression was variable. Nuclear expression of MCM2 was noted in tumor but not mitotic cells of all the MFHs and 26 (72.2%) of the BFHTs, the labeling indices (LIs) being 62.0% in the 28 ordinary types, 38.5% in the 10 myxoid types, and 11.2% in the BFHTs with significant difference. Moreover, the LI was significantly higher for MCM2 than that for Ki-67 in the MFHs of both types (p<0.05). No correlation was noted between the MCM2-LI and P53 expression or apoptotic indices, which were significantly higher in the MFHs than BFHTs (p<0.01). These results indicate that MCM2 would correlate with cell proliferation rather than apoptosis in MFHs, and the expression is ubiquitous in proliferating cells, regardless of the expression of P53. Thus, MCM2 might be a reliable marker of proliferating cells in human MFH.