Patients infected with human immunodeficiency virus (HIV) are at risk for various viral and bacterial infections. Active immunization with currently available vaccines may reduce the risk of some vaccine-preventable diseases in this population. Based on available data, most vaccines used in the United States are safe in HIV-infected adults and children. Their clinical efficacy in these individuals is not well defined, although it appears that patients in the earlier stages of infection are more likely to mount a protective antibody response than those in the later stages. Current guidelines for vaccination in HIV-infected children and adults in the United States have been recommended by the Advisory Committee on Immunization Practices.