Similar to other chronic inflammatory diseases such as rheumatoid arthritis the distribution of macrophage subtypes seems to be disturbed in posttraumatic osteomyelitis. This atypical distribution is clearly locally restricted in osteomyelitis. 27E10-positive macrophages found only during the acute phase of inflammation were reduced in 39%, the 25F9-positive subtype, predominating in the late stage of inflammation, was missing in 33%. The antiinflammatory macrophage RM3/1 was decreased in 40% of the osteomyelitis biopsies. Local suppression of macrophage subsets has to be discussed as one of the reasons for the persistence of chronic inflammatory processes in osteomyelitis.