ĭue to the global rise of liver diseases, tremendous scientific advancement in the field of medicinal plants and finding effective and safe natural hepatoprotective agents is one of the future directions. Thus, most of the hepatotoxic chemicals damage liver cells mostly by causing lipid peroxidation which generates a variety of relatively stable decomposition products, mainly α and β-unsaturated aldehydes such as malondialdehyde (MDA), 4-hydroxy-2-nonenal, 2-propenal and isoprostanes and other oxidative damages resulting in generation of highly toxic reactive oxygen species. Particularly, the presence of CCl 4 results in the generation of tricholoromethyl radicals which induce toxicity in rat liver, it also increases lipid peroxidation in the hepatic cells and eventually damage the liver. Chemicals such as carbon tetrachloride, thioacetamide and galactosamine are mostly used in experimental models to study injury of hepatocytes both in vivo and in vitro conditions. They damage the hepatic tissue or to the liver functions, which can be caused by different factors, such as viruses or bacteria, chronic alcoholism, autoimmune diseases, or by the external action of different hepatotoxic chemicals. Hepatic diseases represent a major public health problem, thus resulting in increased morbidity and mortality all over the world, with available treatment options being very costly. The best antioxidant and hepatoprotective activities were those of EOs from two fine powder fractions (≤100 μm and 100 - 200 μm) was correlated to their high concentration in oxygenated terpenes (70.9% and 46.4%, respectively), when compared to the large particles (200 - 355 μm and ≥355 μm, with 33.3% and 41.8%, respectively) and unsieved powder (37.4%). Also, significantly (p < 0.05) decreased the extent of malondialdehyde (MDA) formation and elevated the activities of superoxide dismutase (SOD) and catalase (CAT) liver in comparison to negative control group. In this research, EOs significantly prevented the increase in serum ALT and AST (p < 0.05), total cholesterol, triglyceride and LDL-cholesterol level in acute liver damage induced by CCl 4 and significant increase level of plasma HDL-cholesterol. Activities of enzymes markers of hepatocellular damage in serum and antioxidant enzymes in the liver homogenates were measured. Compounds that are evaluated for these activities are hydrocarbons and oxygenated terpenes that were identified and quantified by GC/MS. Animals were daily orally treated with the EOs extracted by hydrodistillation from powder sieved at four particle sizes (≥355, 200 - 355, 100 - 200, ≤100 μm) and those of the unsieved powder at dose of 50 mg/Kg for 7 days. The aim of the present study was to evaluate particle size effects on antioxidant and hepatoprotective potential of Eucalyptus camaldulensis essential oils (EO) on CCl 4-induced hepatic damage in Wistar rats. Particle size fractionation by sieving is used to optimize antioxydant potential of natural substances.