A selected group of 13 juvenile-onset insulin-dependent diabetics in mid-late puberty (stages 3-4) and under comparable conditions of metabolic control was studied in order to evaluate the plasma levels of corticosteroid-binding globulin (CBG, transcortin: expressed as the binding capacity for cortisol) in relation to the levels of other glycoproteins and to growth hormone (GH) and prolactin (PRL) responsiveness to provocative tests (arginine infusion and TRH injection, respectively). Further evidence was provided that juvenile-onset diabetics show most frequently enhanced plasma CBG binding capacity; statistical significance with p-values less than 0.01 was attained in comparison to 25 age-matched controls. Among other variables examined, only hemoglobin A1c amd alpha 2-macroglobulin were significantly raised in the diabetic group (p less than 0.01 and less than 0.02, respectively). In our patients growth hormone response to arginine infusion was in the normal range, whereas PRL response to TRH was slightly but significantly supranormal in terms of maximum value and maximum increment above baseline value. No correlation was found between CBG binding capacity and other variables examined. We conclude that raised levels of CBG may occur as an additional alteration of the plasma glycoprotein pattern in juvenile-onset insulin-dependent diabetics. Specific regulatory factors conceivably subserve plasma concentrations of different glycoproteins.