Using surface and deep seawater collected in the sea area of Muroto Cape (Kochi, Japan), desalinated drinking samples of about 1200 hardness were prepared and examined for the effects on the prevention of atherosclerosis in dietary induced hyperlipidemia rabbits. The plasma LDL cholesterol level was lower in the deep seawater group than in the surface seawater group. GPx activity was significantly higher in the deep seawater group than in the control group, while there was no difference between the surface seawater and control groups. The level of LPO was also significantly lower in the deep seawater group than in the control group. The Sudan IV lipid stained area ratio on the inner surface of the aorta was significantly lower in the deep seawater groups than in the control group, while there was no difference between the surface seawater and control groups. The oil red O stained cross section of the aorta in the control and surface seawater administration group foam cells had accumulated to form thick layers, while in the deep seawater administration group, the degree of their accumulation was very low. These results suggested that the deep seawater was useful for the prevention of hyperlipidemia and arteriosclerosis compared to the surface seawater, and it was found that reduction of the LDL cholesterol level and enhancement of GPx activity were involved in its effects.