Forty-nine normoalbuminuric diabetic patients were studied: 22 males and 27 females, in whom urinary heparan sulphate (HS), albuminuria, creatininemia, creatininuria, creatinine clearance, HbA1c and arterial pressure (AP) were determined. Two groups were discerned: group 1, Type 1 DM, diabetic cases (n = 16); and group 2, Type 2 DM diabetic cases (n = 33). Patients were compared with 24 healthy controls: 12 men and 12 women, who showed a mean value +/- SD of 0.36 +/- 0.18 mg/24 h HS with significant differences between males and females (0.43 +/- 0.15 versus 0.28 +/- 0.17, respectively; p = 0.02). The total population of diabetic cases rendered a mean of 0.68 +/- 0.44 and comparison with controls proved highly significant (p < 0.001). Globally, male patients had a mean of 0.82 +/- 0.48 and females 0.54 +/- 0.35, with p < 0.02. Group 1 and 2 values of HS were not significantly different. HS levels failed to correlate either with age, body mass index (BMI), time since onset of diabetes, albuminuria, creatininemia, creatininuria, creatinine clearance, HbA1c or arterial hypertension. To conclude: both normal and diabetic males eliminate a greater quantity of HS than females. Normoalbuminuric diabetic patients of both types eliminate a greater quantity of HS regardless of arterial pressure and time since onset of diabetes.