—In hypertensive heart disease, no data are available on the repair of coronary resistance vessels in patients after long-term ACE inhibitor treatment. Fourteen patients with essential hypertension were studied with coronary flow reserve and with transvenous endomyocardial biopsy before and after 12 months of antihypertensive treatment with perindopril (4 to 8 mg/d, mean 5.9±2.3 mg/d). Left ventricular muscle mass index decreased by 11% (from 145±41 to 128±36 g/m², P=0.04). Maximal coronary blood flow was increased by 54% (from 170±46 to 263±142 mL · min⁻¹ · 100 g⁻¹, P=0.001), and minimal coronary vascular resistance was diminished by 33% (from 0.67±0.21 to 0.45±0.19 mm Hg · min · 100 g · mL⁻¹, P=0.001); consequently, coronary reserve increased by 67% from 2.1±0.6 to 3.5±1.9 (P=0.001). Structural analysis revealed regression of periarteriolar collagen area by 54% (from 558±270 to 260±173 μm², P=0.04) and of total interstitial collagen volume density by 22% (from 5.5±3.8 Vv% to 4.3±3.2 Vv%, P=0.04), whereas arteriolar wall area was slightly but not significantly reduced. Long-term therapy with the ACE inhibitor perindopril induces structural repair of coronary arterioles that is mainly characterized by the regression of periarteriolar fibrosis and associated with a marked improvement in coronary reserve. These findings indicate the beneficial reparative effects of ACE inhibition on coronary microcirculation in hypertensive heart disease.