Hopes to develop apolipoproteins for diagnostic or, even better, therapeuticpurposes are growing. Areas of use may range from arterial disease to AIDS, fertilization programs, neurological or inflammatory disorders, and the like. However, these young members of the large family of circulating proteins still deserve careful study, both in terms of structural and functional properties and of their pathological changes. In addition, related molecules, in particular belonging to the family of enzymes, such as lipases and acyltransferases, offer exciting insight into the mechanisms of regulation of lipid transport and exchange. Described hereis the use of apolipoproteins and enzymes in the diagnosis of coronary and cerebrovascular disease. Structural and functional changes of apolipoproteins are related to lipid transport and binding to different receptors. Further, the development of apolipoprotein drugs and their possible clinical use for vascular and non vascular disease is discussed and finally an overview on lipoprotein transformation processes, expression systems and natural mutants is provided.