P-selectin (CD62P) is a member of the selectin family of cell adhesion molecules. It is expressed on stimulated endothelial cells and activated platelets and mediates leukocyte rolling on stimulated endothelial cells and heterotypic aggregation of activated platelets onto leukocytes. It also mediates heterotypic aggregation of activated platelets to cancer cells and adhesion of cancer cells to stimulated endothelial cells. Using P-selectin knockout mice, the importance of P-selectin-mediated cell adhesive interactions in the pathogeneses of inflammation, thrombosis, growth and metastasis of cancers has been clearly demonstrated. Here we will summarize the current knowledge and highlight the important progress in the biomedical research of P-selectin biology, providing a suitable target for therapeutic interventions developed through both experimental and bioinformatic approaches.