Fatty acid binding proteins (FABP) are small (approximately 13-14 kDa) intracellular proteins with a high degree of tissue specificity. FABPs are a class of cytoplasmic proteins that bind long chain fatty acids. They are abundantly present in various cell types and seem to play an important role in the intracellulair utilization of fatty acids. There are at least six distinct types of FABP, each showing a specific pattern of tissue expression. FABP leaks, due to its small size, rapidly out of ischemically damaged dying cells leading to a rise in serum levels. Liver FABP is a sensitive marker for cell damage of liver cells in vitro and in vivo. Ischemically damaged tissues are characterized histologically by absence (or low presence) of FABP facilitating recognition of such areas. Next to this L FABP is a marker for rapid hepatocyte lysis in vitro (as for example in toxicology assays) and for detection of liver damage during and after transplantation.