Malignant histiocytosis, an affection in which there is proliferation of morphologically atypical histiocytes, traditionally associates high fever, deterioration of the general condition, adenopathy, hepatosplenomegaly, and less frequently, cutaneous lesions. Clinical, radiological, and histological signs of bone involvement are rarely observed, which demonstrates the interest of the case reported of a pure medullary form with massive necrosis and successive bone localisations of the osteolytic type. The clinical picture was completed by the progressive development of adenopathy and hepatosplenomegaly. Multiple chemotherapy, according to the A.V.E.C. procedure, controlled the affection for three months before it became totally ineffective. Survival for twelve months after clinical onset demonstrates the extreme malignancy of the affection.