Immunohistochemical localization of lactate dehydrogenase subunits was studied using a fluorescent antibody technique in porcine liver. Because of the difficulty in demonstrating specific fluorescence of LDH-M in the liver tissue, many fixatives were tested both in frozen and paraffin sections to obtain consistent staining results. Among the fixatives examined, ether-ethanol-acetone mixture in frozen sections gave the best result in demonstrating both subunits in the liver tissue by immunofluorescence. Paraffin sections failed to preserve LDH-M specific fluorescence in this study. Specific fluorescence for LDH-H was observed in the hepatic cell membrane facing the space of Disse, in the lining cells of sinusoids and in the cyto plasm of Kupffer cells. LDH-M specific fluorescence was observed as fine granules in the cytoplasm of hepatic cells.