The present study was undertaken to assess the beneficial effects of a daily consumption of 8 % freeze-dried red-pigmented leafy lettuce (Lactuca sativa) on CVD. C57BL/6J mice were fed a high-fat high-cholesterol diet supplemented with or without red-pigmented leafy lettuce for 4 weeks. The present results showed that the red-pigmented leafy lettuce-supplemented diet significantly decreased the level of total and LDL-cholesterol and TAG in the plasma of the mice. The atherosclerotic index was calculated to be 46 % lower in the mice fed with the lettuce diet compared with the control diet. Lipid peroxidation measured by 2-thiobarbituric acid-reactive substances was markedly reduced in the plasma, liver, heart and kidney of the mice fed the lettuce diet. The content of antioxidants (total glutathione and β-carotene) was significantly increased by lettuce supplementation. The antioxidant defence system by antioxidant enzymes including glutathione S-transferase, glutathione peroxidase, glutathione reductase, superoxide dismutase and paraoxanase in blood or liver tissues was also increased, and showed the improved oxidative stress in the mice fed the lettuce diet. The measurement of tail DNA (%), tail extent moment and olive tail moment indicated that the lettuce diet increased the resistance of hepatocyte and lymphocyte DNA to oxidative damage. The present study showed that the supplementation of a high-cholesterol high-fat diet with 8 % red-pigmented leafy lettuce resulted in an improvement of plasma cholesterol and lipid levels, prevention of lipid peroxidation and an increase of the antioxidant defence system and, therefore, could contribute to reduce the risk factors of CVD.