OBJECTIVE To evaluate renal tubular function in young insulin dependent diabetics. METHODS Plasma uric acid levels, renal urate excretion, uric acid tubular load and uric acid fractional excretion were compared between a group of young diabetics without microalbuminuria (n = 27), between 5.5 and 16.8 years of age, and a control group (n = 22). RESULTS The plasma uric acid levels was lower in the diabetic group than in the control group (2.9 +/- 0.7 vs 3.6 +/- 0.6 mg/dl). The renal excretion of urate was higher in the diabetic group than in the control group (17.6 +/- 4.8 vs 13.6 +/- 5.1 mg/kg/d). The uric acid tubular load was similar in both groups (2.5 +/- 1.0 vs 2.4 +/- 0.7 mg/min/1.73 m2). The uric acid fractional excretion was higher in the diabetic group than in the control group (20.9 +/- 11.9 vs 11.4 +/- 4.8%). No correlation between plasma uric acid level and renal urate excretion with insulin therapy (U/kg/d), metabolic control or the time of evolution was found. CONCLUSIONS These results suggest that, in young diabetics, there is a renal hypouricemia due to tubular defects.