The present study tested the hypothesis that reduced arterial elasticity seen in hypertension is related to increased oxidation of LDL. Fifteen men with borderline hypertension (BHT), with blood pressure values classified as high normal (systolic blood pressure 130-140 mmHg or diastolic blood pressure 85-89 mmHg) were included. The control group comprised 22 men with normal blood pressure values (<135/80 mmHg) matched for age, body size and LDL-cholesterol level. Distensibility of aorta was measured using magnetic resonance imaging, and distensibility of the common carotid artery using ultrasound. Baseline LDL diene conjugation was used as a marker for ox-LDL. Aortic and carotid distensibilities were lower in the BHT men than in controls (1.4 +/- 0.6 vs. 1.9 +/- 0.6%/10 mmHg, p<0.05 for aortic distensibility; 2.9 +/- 0.9 vs. 3.6 +/- 0.6%/10 mmHg, p<0.05 for carotid distensibility). Ox-LDL was significantly higher in the BHT men than in controls (44 +/-15 vs. 28 +/- 8 micromol/L, p<0.01). In univariate analysis, ox-LDL associated with aortic distensibility (r=-0.43, p<0.05). In multivariate analysis, the differences in distensibilities between the groups disappeared when the values were adjusted for ox-LDL. These data show decreased arterial elasticity and increased LDL oxidation in young men with borderline hypertension, and suggest that oxidative modification of LDL particles may play a pathophysiological role in the development of reduced arterial distensibility in hypertension.