Recently, the presence of a soluble form of IL-2 receptor (IL-2RS) in human sera and in supernatants of PHA-stimulated lymphocytes has been demonstrated. It has been suggested that autoimmune diseases could be characterized by a defect in production of IL-2RS, unlike immunoproliferative disorders which are characterized by overproduction. Our aim was to investigate serum IL-2RS levels in 35 newly diagnosed Type 1 diabetic patients, in 25 age-matched healthy blood donors and in five patients with Hodgkin's disease. We found that newly diagnosed diabetic patients have higher IL-2RS levels (424.8 +/- 203 U/ml) than normal controls (252.4 +/- 38.4 U/ml) (p less than 0.005). In 22 out of 35 patients (62.8%) the IL-2RS values were above the higher 95% tolerance limit of controls. Furthermore, the persistence of high IL-2RS levels was observed in 18/35 diabetic patients six months after diagnosis (470 +/- 195.6 U/ml). The increased levels were not correlated with glycaemic and HbA1c levels and patients' age. Our findings suggest a potentially significant role for the released IL-2R in the regulation of IL-2 dependent lymphocyte functions in Type 1 diabetes. The study of IL-2RS in Type 1 diabetes may provide a new tool for the knowledge of cytokine involvement in the disease.