A small- for- gestational age female infant presented with bilateral hypoplastic kidneys at 3 months of age. She developed chronic renal insufficiency. Insulin- requiring, non- autoimmune diabetes was documented at 6 years of age. She had mild steatosis and iron deposition in the liver, and mal- development of pancreas. Genetic studies revealed a heterozygous mutation ( S148L) of the HNF1B gene, compatible with an HNF1B- MODY phenotype ( MODY5). This is the first case of HNF1B- MODY reported from Turkey and represents a particularly severe phenotype of the disease.