Peritoneal macrophages are used as primary macrophages in lots of studies, mainly because they are easy to obtain. Injection of thioglycollate broth i.p. induces inflammatory responses and elicits large numbers of macrophages. This protocol can be used for harvesting resident or thioglycollate-elicited peritoneal cells. Peritoneal macrophages are non-adherent in situ and when they are cultured in dishes, they become adherent so that macrophages may be separated from other types of cells in peritoneal cavity.