Optimal and early control of recent onset, type I diabetes by intensive insulin therapy has been reported to allow insulin withdrawal in about two thirds of subjects treated. We used continuous s.c. insulin infusion (CSII) in the attempt to induce a temporary remission of insulin dependence in 18 newly diagnosed young adult diabetics. After 10 days of optimized glycometabolic control, insulin infusion was stopped and patients were switched to glibenclamide (15 mg/die) plus metformin (1 g/die). Diabetics were considered in remission of insulin dependence when their metabolic control fulfilled the following criteria for at least 3 months: absence of glycosuria, pre- and post-prandial blood glucose less than or equal to 120 and 180 mg/dl, respectively, HbA1c less than or equal to 7%. Insulin therapy could be discontinued for periods of over three months in 11 subjects (61%) and for as long as 18 months in one case. Insulin requirement during CSII was slightly higher in nonremitters (NR) than in remitters (R): 0.36-0.64 vs 0.26-0.41 U/kg/die. After 24 months from CSII, R still showed lower insulin requirement (0.35-0.42 U/kg/die) than NR (0.55-0.75 U/kg/die). Further, the role of some hormonal and immunologic factors was investigated. Plasma C-peptide and glucagon were measured, fasting and 2h after each meal, both on admission and immediately after CSII, when patients were switched to oral therapy. No difference in hormone levels could be detected on admission, whereas, after CSII, mean post-prandial increase of C-peptide over basal was significantly higher in R than in NR (1.18 +/- 0.37 vs 0.22 +/- 0.16 ng/ml, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)