IMPORTANCE Blood pressure reduction and renin-angiotensin-aldosterone system inhibition are targets for treatment of atherosclerosis. The effect of renin inhibition on coronary disease progression has not been investigated. OBJECTIVE To determine the effects of renin inhibition with aliskiren on progression of coronary atherosclerosis. DESIGN, SETTING, AND PARTICIPANTS A double-blind, randomized, multicenter trial (Aliskiren Quantitative Atherosclerosis Regression Intravascular Ultrasound Study) comparing aliskiren with placebo in 613 participants with coronary artery disease, systolic blood pressure between 125 and 139 mm Hg (prehypertension range), and 2 additional cardiovascular risk factors conducted at 103 academic and community hospitals in Europe, Australia, and North and South America (enrollment from March 2009 to February 2011; end of follow-up: January 31, 2013). INTERVENTIONS Participants underwent coronary intravascular ultrasound (IVUS) imaging and were randomized to receive 300 mg of aliskiren (n = 305) or placebo (n = 308) taken orally daily for 104 weeks. Disease progression was measured by repeat IVUS examination after at least 72 weeks of treatment. MAIN OUTCOMES AND MEASURES The primary efficacy parameter was the change in percent atheroma volume (PAV) from baseline to study completion. Secondary efficacy parameters included the change in normalized total atheroma volume (TAV) and the percentage of participants with atheroma regression. Safety and tolerability were also assessed. RESULTS Evaluable imaging data were available at baseline and follow-up for 458 participants (74.7%). The primary IVUS efficacy parameter, PAV, did not differ between participants treated with aliskiren (−0.33%; 95% CI, −0.68% to 0.02%) and placebo (0.11%; 95% CI, −0.24% to 0.45%) (between-group difference, −0.43% [95% CI, −0.92% to 0.05%]; P = .08). The secondary IVUS efficacy parameter, TAV, did not differ between participants treated with aliskiren (−4.1 mm3; 95% CI, −6.27 to −1.94 mm3) and placebo (−2.1 mm3; 95% CI, −4.21 to 0.07 mm3) (between-group difference, −2.04 mm3 [95% CI, −5.03 to 0.95 mm3]; P  = .18). There were no significant differences in the proportion of participants who demonstrated regression of PAV (56.9% vs 48.9%; P = .08) and TAV (64.4% vs 57.5%; P = .13) in the aliskiren and placebo groups, respectively. CONCLUSIONS AND RELEVANCE Among participants with prehypertension and coronary artery disease, the use of aliskiren compared with placebo did not result in improvement or slowing of progression of coronary atherosclerosis. These findings do not support the use of aliskiren for regression or prevention of progression of coronary atherosclerosis. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00853827. Guidelines recommend blood pressure reduction in patients with hypertension with a treatment goal of 140 mm Hg for systolic and 90 mm Hg diastolic blood pressure for most individuals.1 The benefit of additional blood pressure lowering agents in patients who have reached treatment goals has not been established. However, few trials have examined the benefits and risks of further intensifying blood pressure treatment in patients with established coronary artery disease (CAD) who are in the prehypertension range.2,3 Preclinical data demonstrate that renin-angiotensin-aldosterone system (RAAS) activation plays an important role in atherosclerosis4 and that RAAS inhibition may have a direct beneficial effect on the artery wall.5 Conventional RAAS modulating agents result in a compensatory increase in circulating renin levels, which may counteract any vascular benefits.6 Direct renin inhibition enables RAAS modulation without increases in renin activity.7 A potential advantage is supported by evidence of an atheropr otective effect of renin inhibition in animal atherosclerosis models.8- 10 However, enthusiasm for this approach decreased following the demonstration of potentially harmful clinical effects with the. ; Stephen J. Nicholls, George L. Bakris, John J. P. Kastelein, Venu Menon, Bryan Williams, Juergen Armbrecht, Patrick Brunel, Maria Nicolaides, Amy Hsu, Bo Hu, Hui Fang, Rishi Puri, Kiyoko Uno, Yu Kataoka, Dianna Bash, Steven E. Nissen