The expression of cytoplasmic and surface proteins in cultured human skin fibroblasts, human umbilical cord cells obtained after normal delivery on gestation week 38-40, and mesenchymal bone marrow stem cells was compared by the methods of immunocytochemistry and flow cytofluorometry. Bone marrow mesenchymal stem cells expressed a great variety of marker proteins typical of stem and progenitor cells and did not express proteins typical of differentiated cells. Fibroblast-like umbilical cord cells expressed markers of both stem cells and differentiated cells. Fibroblasts of dermal origin were characterized by intensive expression of proteins typical of differentiated cells.