The number of identified monogenic diabetes progressively increases with time even if these forms of diabetes represent less than 5% of the cases. Every monogenic diabetes is characterized by an impairment of Beta cell at various levels. They are good models of diabetes-prone mechanisms. Diabetologists should recognize these forms because the management of the patients could be modified as a function of the genetic anomaly, in terms of either choice of hypoglycaemic agents, prognostic, management of associated manifestations or genetic counselling.