The receptor encoded by the W (c-kit) locus is expressed on the membrane of mouse primordial germ cells, whereas its ligand termed stem cell factor (SCF), encoded by the Sl locus, is expressed on the membrane of somatic cells associated with both the primordial germ cell migratory pathways and homing sites. Using an in vitro short time assay which allows a quantitative measure of adhesion between cells, in the present paper we show that SCF/c-kit interaction can modulate primordial germ cell adhesion to somatic cells. We report that the adhesiveness of 11.5 dpc primordial germ cells to four types of somatic cells in culture (TM4 cells, STO fibroblasts, bone marrow stromal cells and gonadal somatic cells) is significantly reduced by antibodies directed against c-kit receptor or SCF, as well by soluble SCF. This SCF/c-kit mediated adhesion seems independent of SCF-induced tyrosine autophosphorylation of c-kit receptor. Moreover, primordial germ cells showed a poor ability to adhere to a bone marrow stromal cell line carrying the Sl(d) mutation (unable to synthesize membrane-bound SCF). This adhesiveness was not further impaired by anti-c-kit antibody. These results demonstrate that SCF/c-kit interaction contributes to the adhesion of primordial germ cells to somatic cells in culture and suggest that the role played by SCF in promoting survival, proliferation and migration of these cells in vitro and in vivo, demonstrated by several studies, might depend on the ability of the membrane-bound form of this cytokine to directly mediate primordial germ cell adhesion to the surrounding somatic cells.