The aerial parts of Anethum graveolens (dillweed) are used in Iran as a hypolipidemic agent. The scientific basis for its use has yet to be established. In this study the hypolipidemic activity of dill powder and its essential oil (its most important fraction) were evaluated in male Wistar rats (180 +/- 20 g) fed a high cholesterol diet. Anethum graveolens essential oil (AGEO) was prepared by hydrodistillation and analysed using GC/MS. AGEO had a yield of 2% and GC/MS analysis showed that alpha-phellandrene (32%), limonene (28%) and carvone (28%) were its major components. Daily oral administration of AGEO to rats at doses of 45, 90 and 180 mg/kg for 2 weeks significantly and in a dose-dependent manner reduced total cholesterol, triglyceride and low density lipoprotein cholesterol (LDL-C). AGEO also increased significantly high density lipoprotein cholesterol (HDL-C). Anethum graveolens powder when added to the diet of animals showed similar effects on serum lipids. It is concluded that Anethum graveolens has significant lipid lowering effects and is a promising cardioprotective agent.