This report concerns a case in which were presented generalized diffuse osteosclerosis, generalized fibrosis of the bone marrow, an arresting erythroleukoblastic blood picture with numerous "atypical platelets" and primitive cells with megakaryocytoid characteristics and splenomegaly characterized by myeloid metaplasia in which megakaryocytes were numerous. This case is unique in presenting the association of such advanced changes in blood and bone. The French authors, Emil-Weil and Clerc,1in 1902, and Vaquez and Aubertin,2in 1904, first discussed a syndrome characterized by splenomegaly due to myeloid change and a leukemia-like blood picture, which they suggested showed clinical and pathologic differences from leukemia proper (leukemic myelosis). Since then the reports of approximately 70 cases have been contributed in which are recognized certain common characters of this polymorphic, leukemia-like syndrome. Usually there is hepatosplenomegaly due to myeloid metaplasia in which, in addition to leukoblastic cells, erythroblasts are constantly prominent and giant cells