Despite dramatic declines in the incidence of opportunistic infections (OIs) in the United States, they remain an important cause of morbidity and mortality for HIV-infected persons. Previously separate guidelines on the prevention of OIs and on the treatment of OIs have been combined recently into an updated single document; the present article reviews salient changes to and new information contained in this guidance. Chapters on hepatitis B virus infection and tuberculosis have been expanded substantially, and each chapter now includes information on immune reconstitution inflammatory syndrome. In addition, there is detailed discussion on the role of antiretroviral therapy in OI prevention and issues concerning the initiation of antiretroviral therapy during treatment of an acute OI. In the future, these guidelines will likely be maintained as an internet-based document to facilitate wider dissemination and more rapid updates.