The present decade was heralded by the identification of cDNA clones for apo-AI, HMG CoA reductase and the LDL receptor. Today we have descriptions of many other proteins involved in lipid metabolism and of the genes that code for them. Structure and function have been probed by techniques for protein blotting and by in vitro mutagenesis of proteins. The details of gene regulation are now beginning to be unravelled and we can expect exciting new developments in the understanding of how gene expression affects plasma lipoprotein levels. New and powerful techniques have been established for identifying known mutations and for detecting new mutations. Discovery of restriction fragment length polymorphisms have allowed the association between these DNA markers and particular genes involved in lipoprotein metabolism to be probed. The extent to which particular gene loci contribute to the variation in plasma cholesterol levels is being analysed using the methods of genetic epidemiology. With the advent of methods for establishing linkage and physical maps of the human genome, it is now possible to identify the genes responsible for any disorder in which clinical material can be assembled. From this rapidly advancing knowledge it must be anticipated that many new exciting diagnostic and therapeutic possibilities will emerge.