Due to the increasing incidence the diagnosis and therapy of osteomyelitis, especially in the subacute and chronic form is an great challenge for todays medicine. So far there is no scheme for the classification of the different osteomyelitis forms and the resulting possible therapies. The aim of this study was the quantitative analysis of T-cells and their subpopulations als well as macrophages as part of the cell-mediated immunity in osteomylitic bone tissue from biopsies taking from 15 patient suffering from different forms of osteomylitis using monoclonal antibodies for CD3, CD45RO, CD8 and CD68. The results showed that the percent of positiv marked cell compaired to the total ammount of immunocompetent cells varied with CD45R0 22%, CD3 mit 13%, CD68 5,2% and CD8 3,0%. Overall the biopsies proved a significant higher expression of secondary antibodies than the controll group. The literature gives no clear evidence for a precise immunological reaction scheme of the human body suffering from osteomyelitis. Looking at our results we suggest a irregular and increased immun reaction leading to a permanent dysregulation of activator-inhibtor-schemes caused by autoimmunological processes. This might keep up a persistent osteomyelitic reaction of the bone. Further studies should therefore concentrate on the quantification of T-Helper-cells. Schlagwörter: Osteomyelitis, Immunhistologie, Differenzierung