The monography "Genetics of Diabetes Mellitus and its Complications" has been published as a fourth part of the specialized publications "The Horizons of Diabetology". It is a complex work summarizing not only current knowledge about genetic background of common and rare types of diabetes (type 1 diabetes, type 2, diabetes, many forms of monogenic diabetes), but also novel information regarding genetic influences of microvascular and macrovascular complications linked to diabetes.