A preliminary study was performed to investigate the staining characteristics of trabecula. endothelial cells with low density lipoprotein (LDL) and acetylated low density lipoprotein (Ac-LDL) labeled with a fluorescent probe, 1, 1`- dioctadecyl-3,3,3`, 3`- tetramethyl-indocarbocyanine perchlorate (Dil). Trabecular endothelial cells revealed a strong fluorescence with Dil-LDL, which was contradictory to the previous results obtained from other types of endothelial cells. These cells also showed a moderate fluorescence with Dil-Ac-LDL. Scleral fibroblasts and keratocytes showed a moderate to strong fluorescence with Dil-LDL and a weak fluorescence with Dil-Ac-LDL. Corneal endothelial cells revealed a very weak background fluorescence with Dil-LDL and a moderate fluorescence with Dil-Ar-LDL. Therefore, these four kinds of cells could not be definitely differentiated depending only on the staining characteristics with Dil-LDL and Dil-Ac-LDt.