Maturity onset diabetes of the young (MODY) is characterized by a primary defect in insulin secretion and hyperglycemia, nonketotic disease, monogenic autosomal dominant mode of inheritance, age at onset less than 25 years, and lack of auto-antibodies. It accounts for 2-5% of all cases of non-type 1 diabetes. The diagnosis may be made by careful clinical evaluation, but exact subtyping is possible only by genetic analysis. Several genetic factors have been identified as causative agents in MODY, each leading to a different type of the disease. These include the enzyme glucokinase, which causes MODY2, and the transcription factors HNF- 4 alpha, TCF1, I PF-1, TCF2, and NeuroD1, which cause MODY1, 3, 4, 5, and 6, respectively. The genetic findings have important clinical implications, allowing for proper genetic counseling, early diagnosis, and better care of patients.