Background: Cardiovascular problems are a major cause of morbidity and mortality in patients with autosomal dominant polycystic kidney disease (ADPKD). Endothelial dysfunction (ED) and intima-media thickness (IMT) are predictors for the development and progression of atherosclerosis. In the present study, ED and IMT were investigated in patients with ADPKD. Methods: Fifteen hypertensive and 16 normotensive patients with ADPKD with preserved renal function, 16 patients with essential hypertension, and 24 healthy subjects were included in the study. Endothelial function of the brachial artery was evaluated by means of high-resolution vascular ultrasound. Endothelial-dependent dilatation (EDD) was assessed by establishing reactive hyperemia, and endothelial-independent dilatation was determined by using sublingual isosorbide dinitrate. Carotid IMT was measured by means of high-resolution vascular ultrasound. Results: EDD was signiificantly worse in hypertensive patients with ADPKD compared with patients with essential hypertension (9.1% +/- 4.1% versus 12.4% +/- 4.6%; P < 0.05) and even in normotensive patients with ADPKD compared with healthy subjects (13.1% +/- 5.2% versus 18.1% +/- 8.1%; P < 0.01). Moreover, carotid IMT was significantly greater in both hypertensive (0.71 +/- 0.10 mm; P < 0.01) and normotensive (0.57 +/- 0.14 mm; P < 0.001) patients with ADPKD compared with healthy subjects (0.45 +/- 0.10 mm). Conclusion: Both hypertensive and normotensive patients with ADPKD show significant ED and increased IMT, which are predictors of atherosclerosis.