The traditional Mediterranean diet is characterized by a high intake of olive oil, fruit, nuts, vegetables, and cereals; a moderate intake of fish and poultry; a low intake of dairy products, red meat, processed meats, and sweets; and wine in moderation, consumed with meals.1 In observational cohort studies2,3 and a secondary prevention trial (the Lyon Diet Heart Study),4 increasing adherence to the Mediterranean diet has been consistently beneficial with respect to cardiovascular risk.2-4 A systematic review ranked the Mediterranean diet as the most likely dietary model to provide protection against coronary heart disease.5 Small clinical trials have uncovered plausible biologic mechanisms to explain the salutary effects of this food pattern.6-9 We designed a randomized trial to test the efficacy of two Mediterranean diets (one supplemented with extra-virgin olive oil and another with nuts), as compared with a control diet (advice on a low-fat diet), on primary cardiovascular prevention.