Both p130^Cas and c-Cbl have been reported to play critical roles in osteoclast function as downstream targets of c-Src kinase. The purpose of this study is to examine adhesion- and M-CSF-induced tyrosine phosphorylation of these two molecules in prefusion osteoclasts (pOCs) derived from either Src(+/?) or Src(-) mice and to directly compare the roles of p130^Cas and c-Cbl in osteoclast function. Cell attachment of normal pOCs to vitronectin induces tyrosine phosphorylation of p130^Cas and to the much lesser extent of c-Cbl. Treatment with M-CSF results in further tyrosine phosphorylation of both p130^Cas and c-Cbl, suggesting cooperation between v3 integrin and M-CSF receptor, c-Fms, in osteoclasts. However, M-CSF induces tyrosine phosphorylation of c-Cbl, but not p130^Cas in pOCs in suspension, confirming the role of c-Cbl as a down stream effector of c-Fms. This observation also suggests that M-CSF-mediated p130^Cas phosphorylation requires ligand engagement of v3 integrin. In Src-deficient pOCs plated on vitronectin, while M-CSF highly induces Cbl phosphorylation, it does not affect p130^Cas phosphorylation. These results suggest that in osteoclasts, 1) Tyrosine phosphorylation of p130^Cas depends on v3 integrin-mediated cell adhesion, even in the presence of M-CSF; 2) On the other hand, c-Cbl phosphorylation is predominantly activated by M-CSF, and independent of cell adhesion; 3) Lastly, while c-Src is essential for both adhesion- and M-CSF-mediated phosphorylation of p130^Cas it is clearly not required for c-Cbl phosphorylation in M-CSF-treated pOCs. Taken together, p130^Cas and c-Cbl play distinct roles in the signal transduction pathways which mediate cytoskeletal organization in osteoclasts.