The measurement of glycated hemoglobin is central in the monitoring of glycemic control in patients with diabetes. There are at least 30 different laboratory assays commercially available to measure the proportion of HbA1c in blood. In 1995 the IFCC established a Working Group (IFCC WG-HbA1c) to achieve international standardization of HbA1c measurement. The main achievements can be summarized as follows: a) a reference measurement procedure has been established with purified primary calibrators; b) a network of reference laboratories has been developed worldwide; and c) work has begun on implementation of traceability to the IFCC reference system. The IFCC WG-HbA1c recognizes the recommendation of the IFCC-IUPAC Committee on Nomenclature, Properties and Units that the analyte measured by the IFCC reference measurement procedure has been defined as betaN1-deoxyfructosyl-hemoglobin and that the recommended measurement units are mmol/mol. The IFCC WG-HbA1c recommends maintaining the use of the name HbA1c in clinical practice.