A series of 2-substituted indan-1,3-dione derivatives, including alkyl (C-1-C-5), mono- and disubstituted phenyl, and other 2-aryl derivatives, were tested for hypolipidemic activity of CF1 male mice at 20 mg/kg per day. These derivatives reduced both serum cholesterol and triglycerides after 16 days of administration intraperitoneally. 2-(4-Methoxyphenyl)indan-1,3-dione was one of the more active compounds with 41% reduction of serum cholesterol and 58% reduction of serum triglyceride levels on day 16. This activity was confirmed in the rat after oral administration. 2-(2-Methylphenyl)- and 2-(4-chlorophenyl)indan-1,3-dione were effective in reducing serum triglyceride levels 58% and 53%, respectively, in mice. Serum cholesterol on day 16 was effectively reduced 46% by 2-(2,4-dimethylphenyl)indan-1,3-dione. The indan-1,3-dione derivatives were more effective than clofibrate in lowering lipid levels in mice. A more detailed study on the effects of 2-(4-methoxyphenyl)indan-1,3-dione demonstrated that key enzymes in the de novo synthesis of lipids were inhibited by the drug lowering tissue levels of lipids but raising those in the feces. The alterations in lipid content of rat lipoprotein fractions by the drug appeared favorable.