Both the increasing number of immunocompromised patients susceptible to pneumonia, and the development of bacterial resistance are significant problems related to the treatment of pneumonia. The primary outcome of treatment for pneumonia is to tip the balance to a successful host response. An ideal approach would be the combination of immunomodulation and conventional antimicrobial therapy for the treatment of pneumonia. It is of increasing importance to understand the components of innate immunity, before immunomodulatory therapy can be applied to patients. Much of our knowledge of the role of alveolar macrophages, cytokines and chemokines in the pathogenesis of pneumonia is derived from animal studies on experimental pneumonia. This article summarizes current information on the role of an alveolar macrophage (AM) and AM-derived mediators in host defense against pneumonia.