Previously, we have determined that human annexin V (hAV), a Ca2+-dependent phospholipid-binding protein, and not rat AV, binds specifically to small hepatitis B surface antigen (SHBsAg), and that transfection of a rat hepatoma cell line with a construct containing the hAV gene led to hAV expression and conferred susceptibility to hepatitis B virus (HBV) infection. In this work, we have examined the effect of administration of hAV on in vitro binding of SHBsAg to human and to rat hepatocytes and on in vitro HBV infection. The results showed that hAV could bind to human as well as to rat hepatocytes. Because of this property, excess hAV was unable to prevent HBV infection in primary cultures of human hepatocytes. On the other hand, it enabled rat hepatocytes to specifically bind SHBsAg and conferred susceptibility to HBV infection. After infection of primary cultures of rat hepatocytes in the presence of hAV, HBV mRNA, covalently closed circular (ccc) DNA, replicative intermediates, hepatitis B surface antigen (HBsAg), hepatitis B core antigen (HBcAg) and secreted HBV DNA were detected. After infection in the absence of hAV, no markers of HBV replication were detected. Hence, from the present study we conclude that hAV is involved in facilitating HBV entry, leading to successful HBV infection in primary cultures of rat hepatocytes, while it is not effective in preventing HBV infection in primary cultures of human hepatocytes.