HIV infection is associated with an increased risk for developing B-cell lymphoproliferative disorders. The spectrum of disease differs in HIV-infected versus HIV-uninfected persons, with aggressive B-cell non-Hodgkin lymphomas constituting a higher proportion of all lymphoproliferative disorders in the HIV-positive population. Although antiretroviral therapy (ART) has significantly changed the landscape of lymphomas arising in HIV-infected persons, population growth and aging are reflected in the steady increase in non–AIDS-defining cancers. In the ART era, outcomes for HIV-infected lymphoma patients are similar to those of HIV-negative patients. This article reviews the diagnostic features and summarizes current biologic understanding of HIV-associated lymphomas.