Chronic inflammation and oxidative stress have been described as crucial factors in the pathogenesis of atherosclerosis and the occurrence of cardiovascular diseases (CVD). Polyphenols are phytochemicals with established antioxidant properties, and dark chocolate (DC), a highly consumed food, is one of main food sources of polyphenols. Many human studies have suggested a lowering effect of DC on oxidized LDL levels, while its impact on high sensitivity CRP (hs-CRP) -one of the most powerful predictors of coronary artery diseases- are still conflicting. The aim of this study is to determine the preventive properties of (polyphenol-rich DC) PRDC on CVD by testing its effects on hs-CRP and oxidized LDL levels. 54 participants (1858 years) with no history of diabetes, hypertension or CVD took part in a 4-week randomized parallel clinical trial. Participants were assigned daily either 20 g of a placebo DC (with negligible amount of polyphenols; 27 participants) or a PRDC (500 mg of polyphenols; 27 participants). Blood samples were collected at baseline and after 4 weeks. In the PRDC group, results showed a significant decrease in oxidized LDL levels (6.65±16.13, P=0.042), while no significant changes in hs-CRP levels were observed (P=0.23) following the intervention. The decrease in oxidized LDL was not associated with a decrease in LDL levels (P=0.92), and no significant changes in the placebo DC group were noted. These outcomes correspond to the findings of the literature which mostly showed a positive effect of PRDC on LDL oxidation, possibly due to the effects of some polyphenols on scavenging oxygen species. The neutral effects on hs-CRP levels fairly match with many intervention trials on cocoa/DC and inflammation. This suggests that further studies controlling for potential confounding factors and drawbacks affecting the reliability of this marker are needed before refuting a positive effect of PRDC on inflammation.