Hemoglobin A1c (HbA1c) is a minor component of human hemoglobin resulting from a non enzymatic linkage of glucose with the NH2-terminal amino acid of the beta chain of hemoglobin. Under normal conditions, HbA1c represent about 5% of total hemoglobin. The HbA1c blood concentration increases in direct proportion of the duration and degree of hyperglycemia. Available procedures for measuring HbA1c include column chromatography, high pressure liquid chromatography, a colorimetric procedure based on the formation of 5-hydroxymethylfurfural and isoelectrofocusing. In a group of 138 patients, we have confirmed that HbA1c provides a useful means of evaluating the degree of diabetic control: the highest values have been recorded in cases of poor control, the lowest in cases of excellent control. In the latter case, the HbA1c values recorded were not statistically different from those obtained in a control group of 92 non-diabetic subjects. The interest of evaluating this parameter in diabetes is briefly analyzed.