ABSTRACT.Glycosylated haemoglobin or HbA, is a valuable instrument and an objective method to evaluate the metabolic state in the management of diabetes mellitus. This paper summarizes the value of HbA1analysis from the clinical point of view, discussing errors and indications. Only 20% of a group of type I diabetic patients had acceptable HbA1niveau indicating that a lot of work has to be done to achieve normoglycaemia in ordinary diabetics outside the remission period and during pregnancy.