S100-B, is an acidic protein with a molecular weight of 21 kDa belonging to the S100 family. S100-B containstwo EF-hand-type calcium-binding motifs separated by a hinge region with a hydrophobic cleft. S100-B playsan important role in neurodevelopment, differentiation, and brain construction. S100-B has neuroprotectiveeffects, but at high concentrations S100-B is neurotoxic. Extracellular concentration of S100-B increasesfollowing brain damage, which easily penetrates into cerebrospinal fluid in brain damage and then into theblood. S100-B is expressed and produced by astrocytes in vertebrate brains and in the CNS, and the astrocytesare the major cells producing S100-B protein in gray matter, as well as oligodendrocytes are the predominantS100-B in protein producing cells in white matter. The major advantage of using S100-B is that elevations inserum or CSF levels provide a sensitive measure for determining CNS injury at the molecular level before grosschanges develop, enabling timely delivery of crucial medical intervention before irreversible damage occurs. Inaddition, S100-B, which is also present in human melanocytes, is a reliable marker for melanoma malignancyboth in bioptic tissue and in serum.