OBJECTIVE: To determine the effect of oral administration of glycosaminoglycans on metabolic control and albumin excretion rate (AER) in NIDDM patients with increased urinary albumin excretion. RESEARCH DESIGN AND METHODS: Twelve NIDDM hypertensive patients (age 52 +/- 3 years, HbA1c 7.7 +/- 0.2%) on antihypertensive treatment were enrolled in a double-blind placebo-controlled study, assuming either placebo or sulodexide (100 mg/day) for 4 months; at the end of this period, a crossover was performed. We have evaluated routine biochemical parameters plus AER and coagulative function every 2 months. RESULTS: Both plasma fibrinogen (from 4.15 +/- 0.32 to 2.77 +/- 0.47 mmol/l) and AER (from 128.3 +/- 40.6 to 39.6 +/- 11.9 micrograms/min) decreased significantly after treatment with glycosaminoglycans in respect to placebo; moreover, blood pressure control ameliorated, also in the absence of any variation of therapy. CONCLUSIONS: Glycosaminoglycan therapy, likely in association with a satisfactory control of blood pressure values, seems to prevent the progression of diabetic nephropathy in NIDDM.