Patients with aids are at increased risk of opportunistic and non opportunistic infections. It is now known that the incidence can be reduced by prophylactic measures and/or the use of vaccines. HIV infection produces an elevated frequency of severe pneumococcal disease with a rate of bacteriemia caused by Streptococcus pneumoniae 150-300 fold greater than rates reported in non-HIV infected people. For this reason, pneumococcal vaccine should be administered as early as possible in the course of the infection. Besides, the antibody response may be significantly higher for asymptomatic persons. Acute hepatitis caused by hepatitis B virus is milder than in non HIV infected patients but chronic disease is more frequent. The prognosis is worse and there is higher risk for infecting another persons. Hepatitis B vaccine is indicated for all the patients with HIV and negative serology for hepatitis B virus. Influenza vaccine is of limited effectiveness due to the high variability of the virus. Besides, influenza incidence is low among approximately young adults, HIV related immunodeficiency increased influenza risk only minimally, the vaccine is administered yearly and HIV-replication can increase in temporal association with vaccination. For all these reasons, fewer hospitalizations and deaths are prevented making it a far less cost-effective prevention strategy than pneumococcal vaccination. The risk of Haemophilus influenzae infections is elevated, but the vaccine is not routinely recommended because the more frequent serotype in HIV infected patients is b. For these subjects, passive immunization with immunoglobulin may also be necessary to provide protection. In conclusion, pneumococcal and hepatitis B vaccination is a reasonable prevention strategy for HIV infected patients at all stages of immunodeficiency. Influenza and H. influenzae vaccination are not recommended and alternative prevention strategies may be done.