['To study circulating adiponectin concentrations in relation to diabetes duration and endogenous insulin secretion in patients with type 1 diabetes.', 'Patients with haemoglobin A1c (HbA1c) < 6% (reference range 3.6-5.4%) were selected for the study. Twenty-two men and 24 women [age 41.3 +/- 13.8 years (mean +/- SD), diabetes duration 4 months to 52 years] participated. Healthy controls (15 women and nine men, age 41.3 +/- 13.0 years) were also included. Overnight fasting serum samples were analysed for adiponectin, HbA1c, C-peptide and lipoproteins.', 'Significant positive associations were found between adiponectin concentrations and diabetes duration in univariate and multiple regression analyses. Serum adiponectin averaged 9.7 +/- 5.3 [median 8.1, interquartile range (IQR) 3.6] mg/l in patients with diabetes duration less than 10 years and 17.8 +/- 10.7 (median 14.7, IQR 7.5) mg/l in patients with longer duration (P = 0.0001). Among the patients, 24 were without detectable (< 100 pmol/l) and 22 with detectable C-peptide levels (185 +/- 91 pmol/l). C-peptide levels in controls averaged 492 +/- 177 pmol/l. HbA1c was 5.7 +/- 0.6% in patients without detectable C-peptide and 5.6 +/- 0.4% in patients with detectable C-peptide (ns). Serum adiponectin was higher in patients without detectable C-peptide than in patients with detectable C-peptide [17.3 +/- 11.1 vs. 10.6 +/- 5.8 mg/l (P < 0.005)] and in the controls [10.1 +/- 2.9 mg/l (P < 0.001 vs. patients without detectable C-peptide)].'] Is elevated circulating adiponectin in type 1 diabetes associated with long diabetes duration?