Plasma concentrations of fructosamine, an indicator of glycated plasma proteins, were measured in non-diabetic children and children with insulin-dependent diabetes mellitus (IDDM) to see if they also correlate with glycemic control in children as well as in adults. Non-diabetic children aged less than 4 yr had significantly lower plasma fructosamine than non-diabetic children aged 4 or more. Total plasma protein in these children was slightly lower or close to that of older children. There was no difference in fructosamine between non-diabetic children aged 4 or more and healthy adult subjects. Plasma fructosamine in children with IDDM was twofold that of age-matched controls. In children with IDDM, correlations between fructosamine and HbAI (r = 0.799) or HbAIc (r = 0.841) were high. The measurement of plasma fructosamine, which is practical in children because of the small sample volume needed and no influence of HbF, is useful in the management of children with IDDM.