Aim: To examine if cadherins are expressed constitutively in human bone marrow stromal cells (hBMSC) and investigate the regulation of cadherin expression by various osteotropic hormones and local factors. Methods: Cadherin expression was examined in first passaged (secondary) hBMSC as well as in the conditionallyimmortalized human osteoprogenitor cell line (hOP-7). Using a monoclonal antibody (MoAb C-1821) to a cytoplasmic domain common to all known cadherins (pan-cadherin MoAb), cadherins were immunolocalized in first passaged hBMSC as well as in hOP-7 cells. In addition, intense immunostaining for cadherin expression was associated with alkaline phosphatase (ALP) in nodules formed in the high density cultures of hOP-7 cells. Human E-cadherin (HECD) was specifically detected by Weste blotting in extracts of untreated hBMSC using an anti-HECD MoAb 004FD. Results: Differential regulation of cadherin expression by various osteotropic hormones and local factors (parathyroid hormone, dexamethasone,estradiol, prostaglandin E2, basic fibroblast growth factor, and tumor necrosis factor-β) was also observed. In addition, blocking cadherins with the MoAb C-1821 increased basal ALP activity and had an additive effect on 1, 25(OH)2D3-induced ALP activity. Conclusion: Cadherins are expressed in human osteoprogenitor cells and are involved in the osteogenic differentiation. The differential modulation of cadherin expression by osteotropic agents indicates that these agents may regulate osteoprogenitor cells through different cadherins and these cadherins may play different roles.