Liver plays an important role in biological detoxication of xenobiotics. During this process, one can observe the inactivation and successful elimination of metabolites and toxic substances. The metabolic reactions responsible for detoxications include phases I and II. The phase I reactions increase polarity of xenobiotics through inserting new functional groups to xenobiotic molecules, while during phase II conjugation to endogenous hydrophilic molecules results in potent increase in polarity and water solubility. Phase III involves the transport process mediated by transmembranous transporter proteins, which remove a large number of xenobiotics from blood into liver. Oxidative stress and oxidation of lipids may lead to liver injury. Functional impairment of mitochondrial metabolism is associated with intensive production of reactive oxygen species. The underlying mechanisms during mitochondrial dysfunction may lead to cellular necrosis and apoptosis.