Two different reports, including one from our own group, have recently demonstrated the presence of severe chromosomal abnormalities in mesenchymal stem cells (MSC) from patients with myelodysplastic syndromes (MDS). In the present study, we have assessed whether such cytogenetic abnormalities result in functional deficiencies in vitro. We found that both normal and MDS MSC showed similar expression patterns of cell adhesion molecules and extracellular matrix proteins. MDS MSC layers showed the capability to differentiate towards adipocytes, chondrocytes and osteoblasts, and supported the growth of early umbilical cord blood progenitors in a co-culture system. Unstimulated MDS MSC secreted more IL-1beta and after treatment with TNFalpha, they secreted more SCF, as compared to their normal counterparts. The present study demonstrates that, in spite of harboring severe chromosomal alterations, most of the functional properties of MDS-derived MSC remain normal, including their ability to support normal hematopoiesis in vitro.