Prathit A Kulkarni1, Vahid Afshar-Kharghan21Baylor College of Medicine, Houston, Texas, USA; 2The University of Texas, M.D. Anderson Cancer Center, Houston, Texas, USAAbstract: The complement system is an important part of innate immunity; however, as with other parts of the immune system, the complement system can become pathologically activated and create or worsen disease. Anticomplement reagents have been studied for several years, but only recently have they emerged as a viable therapeutic tool. Here, we describe the role of the complement system in a wide array of diseases, as well as the use of anticomplement therapy as treatment for these diseases in animal models and in human clinical trials. Specifically, we will discuss the role of anticomplement therapy in paroxysmal nocturnal hemoglobinuria, glomerulonephritis, and heart disease, including coronary artery disease, myocardial infarction, and coronary revascularization procedures such as percutaneous coronary angioplasty and coronary artery bypass graft surgery.Keywords: complement, paroxysmal nocturnal hemoglobinuria, glomerulonephritis, myocardial infarction, cardiopulmonary bypas