Eosinophilic granuloma (histiocytosis $ imes$) is an uncommon granulomatous disorder affecting the mononuclear phagocytic cell system caused by unknown etiology. When confined to the lungs, it is also known as pulmonary eosinophilic granuloma or pulmonary histiocytosis $ imes$. After the first case was described in 1951 by Farinacci et ai, more 250 cases were reported in the English literature. However only 4 cases has been introduced in our country. We describe two additional cases. In both cases, open lung biopsies are performed for definite diagnosis and examined by immunohistochemical stain for S-100 protein and electron microscopy for ultrastructural identification of Birbeck granule.