We measured in 67 diabetic and 40 non-diabetic children glycosylated haemoglobin levels by both affinity chromatography (Gly Hb) and cation exchange chromatography (Hb A1), glycosylated plasma proteins by affinity chromatography (Gly PP) and glycosylated serum proteins by the colorimetric method of thiobarbituric acid (PSG). There was in the diabetic children a significant linear correlation between these four determinations, as well as between them and the values in mean glycaemias and mean glycosurias. The average Hb A1 over a 20-month observation period was 11.7%; the mean Gly Hb, 12.7%; the mean Gly PP, 5.3%, and the average PSG, 0.77 nmol HMF/mg protein. Glycohaemoglobin levels were within the normal range in only 5% of the cases. About 25% of the diabetic children showed a bad therapeutic compliance, which progressively deteriorated when age and duration of disease increased. Daily insulin requirements and glycosylated haemoglobin levels were significantly higher in diabetic girls than boys, but these differences between sexes did not exist where concentration of glycosylated proteins was concerned. Values in glycohaemoglobin and glycoproteins increased together with age, duration of disease and insulin requirements, existing an inverse relationship with both duration of clinical remission period and socioeconomic level. Motivation, dietetic obedience and, above all, self-control compliance were the variables that exerted the greatest influence on glycohaemoglobin and glycoprotein levels.