To elucidate the mechanism of anemia and leukopenia in the patients with liver cirrhosis, we investigated hematopoietic progenitor cell contents in their bone marrow, and the effects of their sera and blood mononuclear cells on hematopoietic progenitors from normal subjects. While there was no significant difference in the number of marrow CFU-E and BFU-E between the patients with liver cirrhosis and normal subjects, the number of marrow CFU-C was significantly reduced in liver cirrhosis patients. Patients' sera suppressed in vitro colony formation of normal CFU-E, BFU-E, and CFU-C, and the degree of suppression was well correlated with severity of anemia or granulocytopenia. In vitro colony formation of normal hematopoietic progenitor cells was not affected by blood mononuclear cells from liver cirrhosis patients. These results indicate that the appearance of humoral inhibitor(s) of hematopoietic progenitors plays a role in the development of anemia and granulocytopenia in liver cirrhosis.