Apolipoproteins A include apoA-I, apoA-II and apoA-IV. These apolipoproteins are involved in the metabolism of HDL and reverse cholesterol transport. The genes encoding apoA-I, apoA-II and apoA-IV have arisen from a common ancestor. This review describes the structures of the genes encoding apoA-I, apoA-II and apoA-IV, and the structures and functions of the gene products with special reference to the metabolism of HDL and reverse cholesterol transport. Further studies are required to elucidate the full role of apolipoproteins A, especially apoA-II and apoA-IV in HDL metabolism. Analysis of human genetic deficiency and transgenic animal model will be useful for the elucidation of the functions of apolipoproteins A.