Hopes to develop apolipoproteins for diagnostic or, evenbetter, therapeuticpurposes are growing. Areas of use mayrange from arterial disease to AIDS, fertilization programs,neurological or inflammatory disorders, and the like.However, these young members of the large family ofcirculating proteins still deserve careful study, both interms of structural and functional properties and of theirpathological changes. In addition, related molecules, inparticular belonging to the family of enzymes, such aslipases and acyltransferases, offer exciting insight intothe mechanisms of regulation of lipid transport andexchange.Described hereis the use of apolipoproteins and enzymes inthe diagnosis of coronary and cerebrovascular disease.Structural and functional changes of apolipoproteins arerelated to lipid transport and binding to differentreceptors. Further, the development of apolipoprotein drugsand their possible clinical use for vascular and nonvascular disease is discussed and finally an overview onlipoprotein transformation processes, expression systems andnatural mutants is provided.