Human osteosarcoma MG-63 cells were induced into differentiation by hexamethylene bisacetamide (HMBA). Its nuclear matrix proteins were selectively extracted, and subjected to two dimensional gel electrophoresis analysis. The resulted protein patterns were analyzed by Melanie software. There were 12 spots changed remarkably during the differentiation induced by HMBA, nine of which were identified. The up-regulated proteins were identified as MHC class II antigen, interferon-stimulated gene factor 3d, hypothetical protein DKFZp434M2221.1,8-hydroxy-guanine glycosylase homolog ogg1, and vimentin. The down-regulated ones were hnRNP A2/B1 and actin; and two newly expressed proteins under induction were 60S ribosomal protein L21 and ST2 protein. This study suggests that the induced differentiation of carcinoma cells is accompanied with changes of nuclear matrix proteins, and confirms the presence of some specific nuclear matrix proteins associated with carcinoma cell growth and differentiation. The changed nuclear matrix proteins are potential markers for cancer diagnosis or targets for cancer therapy.