The venous system plays a pivotal role in volume and blood pressure homeostasis. We tested the hypothesis that the visco-elastic properties of the peripheral venous system are reduced in patients with (incipient) diabetic nephropathy. Twenty-two normotensive patients with long-term insulin-dependent diabetes mellitus (IDDM), 11 without and 11 with (incipient) nephropathy (eight microalbuminuria and three proteinuria, serum creatinine below 100 mumol l-1), and 14 healthy age/sex matched controls were studied. Forearm venous compliance (VENCOMP) was determined using strain gauge plethysmography and direct intravenous pressure measurements. Furthermore, the venodilatory effect of 0.4 mg sublingual nitroglycerin (NTG) was studied. In comparison with healthy controls, VENCOMP was decreased in patients without and with (incipient) nephropathy, without any differences between the two diabetic groups: 0.059 (0.052-0.066), 0.044 (0.038-0.059) and 0.049 (0.046-0.058) ml 100 ml-1 mmHg-1, respectively (medians and interquartile ranges) (P < 0.05). No differences in the increase of forearm volume after NTG were observed: 0.34 (0.11-0.51), 0.37 (0.19-0.50) and 0.39 (0.20-0.55) ml 100 ml-1, respectively. In conclusion, the visco-elastic properties of the peripheral venous system are reduced in patients with long-term IDDM. This reduction is not related to the presence of nephropathy. No major differences were observed in NTG-induced venodilation between diabetic patients and healthy subjects.