AIM To probe into the feasibility and theoretic basis for the treatment of chronic hepatitis with hyperbaricoxygenation (HBO).METHODS Sixty cases of chronic hepatitis were randomly distributed into an experimental group (n=30)and a control group (n =30). The experimental group was treated with HBO for 6 courses. The controlgroup was treated with commonly used drugs in clinic for 60 days. The function and blood stream graph ofliver were examined and the liver biopsies were made before and after treatment. The routine paraffin slidesof liver tissue were cut, stained with HE, and observed under optical microscope. The ultrathin slides fromparaformaldehyde and glutaraldehyde fixed liver tissue were cut, stained with lead citrate, and observedunder transmission electric microscope. The HBsAg and HBcAg in the experimental group were detected bythe ABC immunohistochemical method before and after treatment.RESULTS In the experimental group the ALT, SB, γ-GT, AKP, IgG and IgM in blood (P< 0.05) and thedegeneration and necrosis of hepatocytes (P