The enzyme, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) controls the biosynthesis of cholesterol. Hypercholesterolemia and atherosclerosis are critical health risk factors. One way of controlling these risk factors is to manipulate regulation as well as degradation of HMGR. At present, a class of compounds called statins, which are HMGR inhibitors, are used for the treatment of hypercholesterolemia. However, statins suffer major setbacks as their use produces more adverse reactions than the desirable one of inhibiting the enzyme. Genetically engineered forms of HMGR are also studied in primitive life forms like bacteria, but detailed investigation of this enzyme in human systems is certainly required. Extensive studies have been made on the regulatory aspects of this enzyme, but no breakthrough is conspicuous in the clinical background to find an alternative treatment for hypercholesterolemia. The immediate need is to find an alternate way of regulating degradation of the enzyme. This review presents the importance of regulation and degradation of the HMGR enzyme in different systems to gain possible insight into alternative schemes for regulating this enzyme and, if these exist, the feasibility of extending them same to studies in mammalian systems. A high degree of similarity exists between mammalian and yeast HMGR. Detailed studies reported on the regulation and degradation of the yeast enzyme also throw more light on the mammalian system, leading to a better understanding of ways of controlling hypercholesterolemia. © Springer-Verlag 2004.