Cell adhesion of osteoblasts and osteoclastic precursors of hematopoietic origin is a prerequisite for osteoclast maturation. We have investigated the relevance of osteoblast–matrix binding and regulation of adhesion molecules to this process. Human osteoblastic cells highly expressed CD44, a major receptor for hyaluronan present in the surrounding bone matrix. Crosslinking of CD44 on osteoblastic cells with specific antibodies augmented the expression of intercellular adhesion molecule (ICAM)‐1 and vascular cell adhesion molecule (VCAM)‐1. Hyaluronan, the major ligand of CD44, also up‐regulated ICAM‐1 expression. Stimulation of CD44 on osteoblastic cells amplified their adhesion to monocytic cells through ICAM‐1 and VCAM‐1. These results suggest that such crosstalk among distinct adhesion molecules may be relevant to bone metabolism, including osteoclastogenesis.