Mesenchymal stem cells (MSCs) retain both self-renewal and multilineage differentiation capabilities. Despite wide therapeutic potential, many aspects of human MSCs, particularly the molecular parameters to define the stemness, remain largely unknown. Using high-density oligonucleotide micro-arrays, we obtained the differential gene expression profile between a fraction of mononuclear cells of human umbilical cord blood (UCB) and its MSC subpopulation. Of particular interest was a subset of 47 genes preferentially expressed at 50-fold or higher in MSCs, which could be regarded as a molecular foundation of human MSCs. This subset contains numerous genes encoding collagens, other extracellular matrix or related proteins, cytokines or growth factors, and cytoskeleton-associated proteins but very few genes for membrane and nuclear proteins. In addition, a direct comparison of this microarray-generated transcriptome with the published serial analysis of gene expression data suggests that a molecular context of UCB-derived MSCs is more or less similar to that of bone marrow-derived cells. Altogether, our results will provide a basis for studies on molecular mechanisms controlling core properties of human MSCs.