We report on 12 patients who fulfilled the FAB diagnosis criteria of chronic myelomonocytic leukemia (CMML). Some clinical findings (splenomegaly) as well as biological parameters (WBC count, cellularity of bone marrow sections, presence of dyserythropoiesis in bone marrow smears) were subjected to particular analysis. This allowed the assignment of each patient onto one of three separate hematological syndromes: (1) RA or RAEB with monocytosis, (2) myelomonocytic dysplasia (a novel syndrome) and (3) true CMML. Such separation may have distinct prognostic significance and may, therefore, predict life expectancy.