This manual for doctors contains information on the genetics of diabetes mellitus (DM) type 1 and 2 and genetic syndromes associated with diabetes in childhood and adolescence. The concept of diabetes as hyperglycemia syndrome, including many independent nosological forms of the disease, is given Presented a new classification of SD. The main methodological approaches used in the study of the genetics of diabetes, types of inheritance and molecular genetic foundations of the development of each nosological form of the disease . are discussed. Empirical risk assessments are given, methods of individual risk assessment are presented on the basis of immunological, molecular-genetic studies, hormonal-metabolic tests . The information set out in the manual is the basis for medical genetic counseling and prevention of the development of the disease in families of patients with diabetes, depending on the nosological form. The manual is intended for endocrinologists, diabetologists, geneticists and general practitioners.