 Lycopene, a carotenoid mainly found in tomato-based food products, has strong antioxidant properties relative to other carotenoids and has been postulated to play a role in the prevention of coronary heart disease through a variety of mechanisms. Lycopene cooked and consumed in oil mediums is optimal for not only its efficient absorption, but also its potential clinical effectiveness. Studies have also linked serum lycopene with the early stages of atherosclerosis, as measured by carotid artery intima-media thickness IMT, a noninvasive ultrasound examination of the carotid arteries and potential surrogate endpoint for subsequent cardiovascular morbidity and mortality used in previous clinical trials of vitamin supplements. Short-term intervention studies of lycopene supplements are limited, having explored mechanisms through which lycopene or its readily absorbable food sources may increase plasma lycopene or induce changes in other relevant biochemical markers impacting the subsequent risk of coronary heart disease. Ateronon is a lycopene supplement developed with the understanding that the potential clinical effectiveness of lycopene is impacted by its bioavailability. A single daily 7 mg tablet of Ateronon provides more bioavailable lycopene than diet alone, is absorbed efficiently, and completely inhibits the atherogenic lipid oxidation processes in subjects. Clinical studies suggest that short-term treatment with Ateronon among those with coronary heart disease leads to favorable reductions in lipid levels, lipoprotein oxidation, blood pressure, and Rose-Blackburn scores. Therefore, we will conduct a randomized, double-blind, placebo-controlled clinical trial of 7 mg Ateronon taken daily for 1 year among 200 patients aged 50 years with stable coronary heart disease. This clinical trial is a collaborative effort between the Division of Preventive Medicine and the Vascular Medicine Program in the Division of Cardiology. Our primary aim is whether taking Ateronon for 1 year is associated with favorable changes in carotid IMT. Secondary aims expand to whether Ateronon leads to favorable 1-year changes in coronary biomarkers related to oxidative stress and endothelial dysfunction; blood pressure; plasma carotenoids; AtheroAbzyme levels; and other traditional coronary biomarkers. This clinical trial of Ateronon seeks to improve our understanding of various mechanisms through which Ateronon, a concentrated and highly bioavailable form of lycopene, may reduce the risk of developing coronary heart disease. 