The vast majority of research about HDL (high-density lipoprotein) has for decades revolved around the possible role of HDL in atherosclerosis and its therapeutic potential within cardiovascular disease prevention; however, failures with therapies aimed at increasing HDL cholesterol has left questions as to what the role and function of HDL in human health and disease is. Recent observational studies have further shown that extreme high HDL cholesterol is associated with high mortality leading to speculations that HDL could in some instances be harmful. In addition, evidence from observational, and to a lesser extent genetic studies has emerged indicating that HDL might be associated with the development of other major noncardiovascular diseases, such as infectious disease, autoimmune disease, cancer, type 2 diabetes, kidney disease, and lung disease. In this review, we discuss (1) the association between extreme high HDL cholesterol and mortality and (2) the emerging human evidence linking HDL to several major diseases outside the realm of cardiovascular disease.