In July 1997, the American Diabetes Association (ADA) has published new recommendations for the diagnosis and classification of diabetes mellitus. Except for gestational diabetes they should be identical to the new WHO recommendations (not yet published). From now on, only the fasting glucose should be used for clinical routine. The oral glucose tolerance test is no longer recommended for this purpose. The diagnostic cut-off level for fasting glucose was decreased from 140 mg/100 ml (venous plasma) to 126 mg/dl, and the range between 110 and 125 mg/100 ml was defined as impaired fasting glucose (IFG), a new diagnostic category introduced in analogy to impaired glucose tolerance (IGT). The lower diagnostic cut-off level for fasting glucose has been proposed because the risk of developing diabetic late complications (predominantly at the vascular system) is already increased in blood glucose ranges thought to be normal. The diagnostic criteria for gestational diabetes are unchanged and still discrepant between ADA and WHO. The two major forms of diabetes should be designated only as type 1- and type 2-diabetes with respect to etiology and pathogenesis. Type 1-diabetes was subdivided into an immune-mediated and into an idiopathic form. MODY (maturity-onset type diabetes in young people) was listed separately from type 2-diabetes under the category of genetic defects of beta-cell function, also mitochondrial diabetes (maternally inherited diabetes and deafness). Malnutrition-related diabetes has been omitted as a major form of diabetes.