Recurrent bacterial pneumonia was recently added to the definition of the acquired immunodeficiency syndrome (AIDS), based on the observation that bacterial pneumonia rates have been increased in human immunodeficiency virus (HIV)-infected persons and are indicative of immunosuppression in this population. Nonetheless, risk factors for bacterial pneumonia among HIV-infected persons remain largely uninvestigated. Identification of risk factors that may be associated with bacterial pneumonia can guide development of future interventions and further clarify target groups for such interventions. From a methodological viewpoint, diagnostic algorithms need to be further standardized to provide comparable estimates of disease incidence. Epidemiologic studies will also need to address the effectiveness of chemoprophylaxis and vaccine interventions in HIV-infected populations. Since clinical trials will not be feasible for testing efficacy of interventions that are already recommended, observational data will be critically important in guiding clinical practice.