Intercellular Adhesion Molecule 1 (ICAM-1), also known as CD54, is a nearly ubiquitous transmembrane glycoprotein which is typically expressed on endothelial cells and cells of the immune system and plays a key role in leukocyte migration and activation. It binds to integrins of type CD11a/CD18, or CD11b/CD18 and is also exploited by rhinovirus as a receptor. Soluble ICAM-1 (sICAM-1) promotes angiogenesis and serves as an indicator of vascular endothelial cell activation or damage. It also functions as an inhibitor of transmembrane ICAM-1 mediated activities such as monocyte adhesion to activated endothelial cells and sensitivity of tumor cells to NK cell-mediated lysis. Monitoring of sICAM-1 levels in serum provides more detailed insights in several pathological situations such as cardiovascular disease, type 2 diabetes, organ transplant dysfunction, oxidant stress, abdominal fat mass, hypertension, liver disease, and certain malignancies.