Three gena of mosquitoes were fed with human blood infected with hepatitis B virus (HBV) artificially. When blood in the stomach was completely digested, mosquitoes were used to bite monkeys Tupaia Belangeri. A month after biting, venous blood samples were taken from the monkeys to detect serum HBsAg, HBeAg, Anti-HBs and Anti-HBc. Among 29 test monkeys, 9 were HBV infective serum markers positive. In 4 of 16 test monkey liver biopsies, acute inflammatory changes were found with Hematoxylin-Eosine staining. In the hepatic cells, HBsAg and HBcAg were detected by immunohistochemical double-labeling assays, and HBV-DNA was also positive by in situ hybridization in monkey liver sections. These results provided an evidence for the possibility of transmission of HBV through mosquitoes and suggest its epidemiological significance in mosquito infested areas.