Hematuria is not described as a common finding in diabetic nephropathy, and may suggest nondiabetic renal disease. We reviewed the records of 59 children and adolescents with insulin-dependent diabetes mellitus referred to the Children's Kidney Center from 1983 to 1992. Fifty-two patients had clinical and/or biopsy evidence of diabetic nephropathy; 18/52 (35%) had microscopic hematuria at the time of referral. Patients with hematuria on presentation were referred for: hypertension (61%), proteinuria (61%), and decreased glomerular filtration rate (GFR) (11%). For patients without hematuria on presentation, reasons for referral included hypertension (79%), proteinuria (56%), and decreased GFR (3%). When comparing patients with and without hematuria, those with hematuria had a significantly longer duration of diabetes (12.8 +/- 3.1 versus 10.8 +/- 3.7 years, p < 0.05). The groups did not differ significantly with regard to age (18.3 +/- 1.8 versus 17.1 +/- 2.9 years), height (162.2 +/- 10.4 versus 159.3 +/- 11.3 cm), weight (63.9 +/- 10.9 versus 59.4 +/- 14.8 kg), systolic blood pressure (137.2 +/- 11.9 versus 133.2 +/- 13.2 mm Hg), diastolic blood pressure (85.6 +/- 7.6 versus 83.9 +/- 13.4 mm Hg), serum creatinine (1.0 +/- 0.18 versus 1.0 +/- 0.43 mg/dL), blood urea nitrogen (15 +/- 5 versus 13 +/- 4 mg/dL), glomerular filtration rate (117 +/- 34 versus 117 +/- 46 mL/min/1.73 m2), 24-h urine protein (2311 +/- 3862 versus 570 +/- 476 mg/day), or microalbuminuria (75 +/- 41 versus 34 +/- 35 micrograms/min). We detected a significant association between retinopathy and microscopic hematuria (sensitivity 47%, specificity 82%, p < 0.05), but no association between labstix proteinuria or sex and hematuria.(ABSTRACT TRUNCATED AT 250 WORDS)