To test whether HLA histocompatibility phenotypes might be associated with circulating hepatitis B surface antigen (HBsAg), we performed chi-square test with Yate's correction and Fisher's exact test on findings in 315 normal healthy hospital staffs with known HLA types and HBsAg status. A significant relation between locus A of HLA types and HBs antigenemia was demonstrated, with negative association suggested between A1, AW23, A26, A29, +AW30 +AW31 and AW32 types and HBs antigenemia. Another significant relation between locus B of HLA types and HBs antigenemia was shown, with negative association suggested between B7, B8, BW21, BW44 and BW49 and HBs antigenemia. There was no significant relation between locus C of HLA type and HBs antigenemia, but type CW4 was revealed to have a relative risk of 2.11. Therefore, previous suggestion that both susceptability and resistance to hepatitis B virus infection may be in part genetically determined and previous observation of population differences in HBsAg prevalences could be interpreted by these findings.