Recent studies reported an increased expression of osteopontin (OPN) in metastatic breast cancer cells, but the mechanisms modulating OPN production and the interaction of the cells with the secreted protein are far from clear. In this work, we utilized as an experimental system the cell line MDA-231 and we showed that HGF and M-CSF significantly enhance their adhesion onto OPN. Furthermore, in the presence of HGF and M-CSF, MDA-231 cells can adhere when plated onto BSA via increased OPN secretion. Moreover HGF and M-CSF induce de novo synthesis of OPN. In conclusion, these data suggest that HGF and M-CSF stimulate OPN production by MDA-231 cells, and that OPN is subsequently used as a substrate for cell adhesion.