One of the major functions of mononuclear phagocytes, i.e., monocytes and macrophages, is the phagocytosis and killing of microorganisms. To obtain more insight into the pathogenesis of infectious diseases and to develop new therapies against these diseases, a better understanding of the antimicrobial mechanisms employed by mononuclear phagocytes is essential. The present review gives a short description of the mononuclear phagocyte system and summarizes various methods that are used to study the antimicrobial mechanisms of mononuclear phagocytes.