Parameters of renal hemodynamics have been determined in 30 male patients with diabetes mellitus, lasting for 1-24 months (mean 0.9 +/- 0.7 year), and in 19 healthy men of the same age. Patients' age ranged from 17 to 33 years (mean 27.5 +/- 5.0). All examined subjects have been normotensive (according to WHO criteria). Glomerula filtration rate with the aid of 51CrEDTA, and ERPF with 125I-hippurate have been determined. Mean GFR values have been significantly higher in diabetics than that in healthy men (142.9 +/- 29 vs 118 +/- 20 ml/min per 1.73 m2). Hyperfiltration (GFR over 140 ml per minute) has been found in 15 patients (50%). ERPF has also been higher in diabetic patients (929.2 +/- 230 vs 821.5 +/- 192 ml/min). This difference has been insignificant. No correlation between arterial blood pressure and GFR, ERPF, filtration fraction (FF), and RVR has been found.