The eosinophilic granuloma is part of the histiocytosis X classification, having a common histological substratum, the granuloma, which is characterized by a proliferation of histiocytes (reticulo-endothelial cells) and a cytoplasmic inclusion body (the X body) whose étiopathogenic significance is not yet established. These histiocytes are accompanied by other cells and in particular granulocytes, the majority of which are eosinophils. Histiocyte proliferation leads to a destruction of bone which is the organ preferentially affected. At first there is osteolysis (this explains the lacunar aspects seen radiologically) followed by sclerosis. The clinical classification established by Lichtenstein in 1953 outlines the tissue form (eosinophil granuloma), the acute disseminated form (Letterersive) and the chronic disseminated form (Hand-Schüller-Christian). This classification is still accepted today but it needs to be refined to include the transitionary forms, and solitary bone granulomas whose long terme evolutive nature it is impossible to measure clinically, biologically, or histologically. From our observation we note that therapy (surgery, radiotherapy, chemotherapy) is effective in controlling the acute growth spurts in a majority of the cases but does not seem to effect the potential long terme evolution.