Subjects at risk of infection with human immunodeficiency virus (HIV) are also at high risk of acute and chronic hepatitis B virus (HBV) infection. HIV is associated with higher HBV viraemia and with the risk of HBV reactivation, chronic active HBV infection, cirrhosis and death. Therefore, hepatitis B vaccination is recommended for all HIV-infected subjects lacking prior immunity. However, the immune response to hepatitis B vaccine is frequently suboptimal in this population. High CD4+ cell counts and low HIV viraemia are well known factors associated with a better rate of response. Moreover, higher hepatitis B vaccine doses and/or prolongation of the vaccination schedule, as implemented for patients with immune deficiencies other than HIV, may be considered. New vaccination cycles should be considered if post-vaccination titers of antibodies to hepatitis B surface antigen are < 10 mIU/mL ( < 10 UI/L). The immunization of all young and middle-aged adults appears to be the most useful strategy to protect all patient-populations at high risk of sexually transmitted diseases.