Simultaneous administration of 3-hydroxy-3-methylglutaric acid (HMG) for 4 weeks to rats fed 20% saturated fats prevented rise of serum cholesterol, triglycerides, and phospholipids. Except phospholipids, other liver lipids were significantly decreased. HMG administration for 4 weeks along with atherogenic diet significantly decreased cholesterol and phospholipids of serum, liver, aorta, and heart. The phospholipids of epididymal fat and brain were also significantly lowered. The triglyceride levels in serum, liver, and epididymal fat were significantly decreased. The maximal hypolipidemic effect of HMG was observed in serum.