The human immunodeficiency virus (HIV) and the hepatitis B virus share common routes of transmission, and hence, coinfection with these two viruses is common. Chronic hepatitis B does not influence the progression of HIV disease or the response to highly active antiretroviral therapy. It is clear, however, that HIV infection does impact the course of hepatitis B, as higher rates of chronic carriage, lower seroconversion rates, and accelerated progression towards cirrhosis have been observed. Vaccination against hepatitis B is less effective in HIV-infected individuals. Coinfected subjects have a poor response to interferon therapy. Lamivudine is more effective in coinfected subjects but must not be used as monotherapy because of the risk of resistance developing. Combination therapy with lamivudine and tenofovir has shown promise and is currently being investigated in clinical trials, while new drugs and other combinations are in development.