L-selectin, also known as CD62L, is a cell adhesion molecule found on the cell surface of leukocytes, and the blastocyst. L-selectin belongs to the selectin family of proteins, which recognize sialylated carbohydrate groups containing a Sialyl LewisX (sLeX) determinant. L-selectin plays an important role in both the innate and adaptive immune responses by facilitating leukocyte-endothelial cell adhesion events. L-selectin is also expressed by lymphoid primed hematopoietic stem cells and may participate in the migration of these stem cells to the primary lymphoid organs. L-selectin is expressed on embryonic cells and facilitates the attachment of the blastocyst to the endometrial endothelium during human embryo implantation. It is cleaved by ADAM17. L-selectin expressed on CD4 T lymphocytes has been implicated in mediating adhesion and entry of HIV. Deficiency epithelial expression of L-selectin ligands has been associated with infertility, while increased expression has been implicated in ectopic pregnancies. The adhesive properties of L-selectin have been shown to contribute to cancer progression.