Magnesium (Mg) modulates blood lipid levels, atherogenesis, and atherosclerosis in rabbits, when supplemented to diet. We have recently reported that a high concentration (50 g/L) of Mg sulfate fortification of drinking water attenuates atherogenesis in male and female LDL-receptor-deficient mice fed a high-cholesterol diet. The aims of the current study were to examine whether lower concentrations and another Mg salt could also have such an antiatherogenic effect. Thirty male LDL-receptor-deficient mice were divided into three groups (n=10 in each group). The mice received either distilled water or water fortified with 0.83 g or with 8.3 g Mg-chloride per liter. In the first (27 wk) and second (5 wk) stages of the experiment, the mice received normal chow and Western-type diet, respectively. Blood was drawn for determination of plasma Mg, calcium, and lipid levels. The extent of atherosclerotic lesions was determined at the aortic sinus. Magnesium-chloride fortification of drinking water did not result in higher plasma Mg concentrations, whereas a trend toward lower plasma calcium concentrations did not reach statistical significance. Even though plasma lipid levels were similar at the beginning and the end of the study, there were decreased plasma cholesterol and triglyceride levels in the Mg groups after stage I. The atherosclerosis extent at the aortic sinus was significantly decreased in the 8.3-g Mg-chloride/L group (23,437 +/- 10,083 micron2) compared with the control group (65,937 +/- 31,761 microm2). There was also a trend toward lower atherosclerosis extent at the aortic sinus in the 0.83-g Mg-chloride/L group. An additional Mg salt (Mg-chloride) fortification of drinking water is capable of inhibiting atherogenesis in male LDL-receptor-deficient mice. That is done in a lower concentration of Mg than previously reported.