The main objective of this study was to assess whether aspirin 100 mg QD can improve blood pressure (BP) control and endothelial function in subjects with arterial hypertension (AH) and hypercholesterolaemia. In total, 21 patients of both sexes (52.1+/-11.5 years) with treated AH and hypercholesterolaemia on antihypertensive and statin therapy were included in the treatment group. In the control group, 20 matched patients of both sexes (51.3+/-12.7 years), but without statin therapy, were recruited. Treatment group subjects received aspirin (100 mg QD) for a duration of 12 weeks at randomization (Treatment phase-1), followed by single blind matching placebo for 12 weeks (Placebo phase) and then again received aspirin (100 mg QD) for an additional 12 weeks (Treatment phase-2). The control group participated in Treatment phase-1, but did not continue Placebo phase and Treatment phase-2. At randomization and at the end of each study phase, mean 24-h systolic BP (SBP) and diastolic BP (DBP) were assessed by 24-h ambulatory blood pressure monitoring (ABPM) and endothelium-dependent (flow mediated, FMD) and -independent (nitroglycerin induced, NTG) vasodilatations of brachial artery were measured using high-resolution ultrasound. In Treatment phase-1, reduction of SBP and DBP (DeltaSBP 5.7+/-2.6 mmHg, P=0.008; DeltaDBP 3.8+/-1.7 mmHg, P=0.014) and improvement of FMD (4.1+/-0.6%, P=0.019), in Placebo phase an elevation of SBP and DBP (DeltaSBP -6.2+/-2.9 mmHg, P=0.002; DeltaDBP -4.2+/-1.9 mmHg, P=0.031) and worsening of FMD (-3.8+/-0.9%, P=0.027), and in Treatment phase-2 reduction of SBP and DBP (DeltaSBP 4.9+/-2.3 mmHg, P=0.005; DeltaDBP 4.1+/-1.3 mmHg, P=0.024) and improvement of FMD (4.5+/-1.3%, P=0.009) were observed in the treatment Group but not in the control group. Addition of low-dose aspirin to antihypertensive medications and statins in hypertensive and hypercholesterolaemic subjects can reduce both SBP and DBP by improvement of endothelial function.