Abstract. E-selectin is an inducible endothelial cell adhesion molecule for neutrophils which functions as a Ca2+-dependent lectin. Using a recombinant, antibody-like form of mouse E-selectin, we have searched for glycoprotein ligands on mouse neutrophils and the neutrophil progenitor cell line 32D cl 3. We have identified a 150-kD glycoprotein as the only protein which could be affinity-isolated with soluble E-selectin from [3sS]methionine/[35S]cysteine-labeled 32D cl 3 cells. Binding of this protein was strictly Ca2÷-dependent, was blocked by a cell adhesionblocking mAb against mouse E-selectin, and required the presence of sialic acid on the 150-kD ligand. This glycoprotein was also afffinity-isolated from mature neutrophils, in addition to a minor component at 250 kD, but could not be isolated from several other nonmyeloid cell lines. The 150-kD glycoprotein was the only protein from 32D cl 3 cells, which was detectable by silverstaining after a one-step affinity-isolation.