Several epidemiological and clinical studies have evaluated the effects of a Mediterranean diet (Med-Diet) on total cardiovascular mortality, and all concluded that adherence to the traditional Med-Diet is associated with reduced cardiovascular risk. However, the molecular mechanisms involved are not fully understood. Since atherosclerosis is nowadays considered a low-grade inflammatory disease, recent studies have explored the anti-inflammatory effects of a Med-Diet intervention on serum and cellular biomarkers related to atherosclerosis. In a pilot study of the PREvencion con DIeta MEDiterranea (PREDIMED) trial, we analysed the short-term effects of two Med-Diet interventions, one supplemented with virgin olive oil and another with nuts, on vascular risk factors in 772 subjects at high risk for CVD, and in a second study we evaluated the effects of these interventions on cellular and serum inflammatory biomarkers in 106 high-risk subjects. Compared to a low-fat diet, the Med-Diet produced favourable changes in all risk factors. Thus, participants in both Med-Diet groups reduced blood pressure, improved lipid profile and diminished insulin resistance compared to those allocated a low-fat diet. In addition, the Med-Diet supplemented with virgin olive oil or nuts showed an anti-inflammatory effect reducing serum C-reactive protein, IL-6 and endothelial and monocytary adhesion molecules and chemokines, whereas these parameters increased after the low-fat diet intervention. In conclusion, Med-Diets down-regulate cellular and circulating inflammatory biomarkers related to atherogenesis in subjects at high cardiovascular risk. These results support the recommendation of the Med-Diet as a useful tool against CVD.