Diabetes mellitus is recognized as one of the most significant public health problems in the world today. The World Health Organization (WHO) has estimated that worldwide some 3 million deaths per year are attributable to this disease, the majority of which are from type 2 diabetes. Moreover, the prevalence of type 2 diabetes specifically is steadily rising. According to a recent study from the US Centers for Disease Control and Prevention, the incidence of diagnosed diabetes in the US alone has nearly doubled over the last 10 years, and globally WHO estimates the prevalence worldwide to reach 366 million by the year 2030, more than double that of 2000. Genetic factors appear to play a role in determining an individual’s risk of developing diabetes. It is hoped that genetic studies will ultimately identify key genetic elements that help determine susceptibility to diabetes, disease progression, and responsiveness to specific therapies, as well as help identify novel targets for future intervention. A substantial number of genetic loci, gene polymorphisms, and mutations have already been reported as having variable degrees of association with one or other type of diabetes (type 1, type 2, maturity onset diabetes of the young [MODY]), while others appear to be involved in response to antihyperglycemic agents. We have compiled the following glossary of genetic and genomic terms relating to diabetes, which we hope will prove a useful reference to researchers and clinicians with an interest in this disease. This is by no means an exhaustive list, but includes many of the genetic loci and variants that have been studied in association with diabetes.