Background: Maturity-onset diabetes of the young' type 5 (MODY5), a type of dominantly inherited diabetes mellitus and nephropathy, has been associated with mutations of the hepatocyte nuclear factor-1 (HNF-1beta) gene. Objective: To describe clinical and genetic findings in the first Vietnamese case 'with HNF-1 beta mutations. Patient The proband with diabetes diagnosed at 14.5 years of age and nondiabetic kidney disease who were described. Methods: descritive study, case report. Genomic DNA were extracted from wec of whole blood and NHF-1beta mutation was performed using PCR and direct sequencing. Results: The proband is heterozygous for an HNF-1beta missense mutation, S148L. This CT mutation at nucleotide 443 (c.443CT) results in the substitution of the amino acid leucine for serine at codon 148 (p.Ser148Leu). This result confirms a diagnosis of renal cysts and diabetes (RCAD). Pancreas atrophy .was observed using abdominal CT. Conclusions: Maturity-onset diabetes of the young type 5 encompasses a wide clinical spectrum. Analysis for mutations of HNF-1beta is warranted, in nonobese patients with diabetes and slowly progressive nondiabetic nephropathy, particularly when pancreatic atrophy.