This study of the history of 117 cases of agnogenic myeloid metaplasia with myelofibrosis underlines the importance of anatomo-pathological and radiological parameters for prognosis. Histological staging of bone and bone marrow lesions at time of diagnosis enables one to confirm long survival of cases with hyperplasia (Group I) and more severe prognosis for advanced myelofibrosis (that is both groups II and III considered together) but does not enable to establish a significative difference between medium survival of cach group II and III considered separately. Those medium survivals estimated are the following: 82 months for group I; 60 months for both groups II and III. Thus, it is logical to consider together these two groups among which one can distinguish two anatomoclinical forms. One is characterized by bone marrow hyperplasia with reticulin myelofibrosis and is usually associated with large spleen and even in some cases with polycythemia but without radiologic bone lesions; the other is characterized by bone marrow of medium or hypoplasic constitution fibrosis, with or without osteosclerosis and with radiologic bone lesions of mode-rate or important extension (respectively 16.9 p. cent of cases) and is usually associated with pancytopenia.