Lecithin:cholesterol acyltransferase (LCAT) is a plasma enzyme that catalyzes esterification of plasma lipoprotein unesterified cholesterol, and plays a central role in maintaining reverse cholesterol transport through action with high density lipoprotein (HDL) and Cholesterol ester transfer protein (CETP). Cloned cDNA sequence of LCAT, consisted of about 1400 base pair which codes 416 amino acids, revealed high content of alpha-helix and beta-sheet, identity of amino acid sequence with various lipases, and putative structure of catalytic sites and mechanism of enzymatic action is proposed. Close relationship between location of gene mutation and severity of clinical and biochemical characteristics revealed by gene analysis in patients of LCAT deficiency and Fish eye disease is summarized.