Repopulation kinetics of erythrocytes and neutrophils and replacement of hematopoietic progenitors were studied in genetically anemic (WB x C57BL/6)F1-W/Wv (WBB6F1-W/Wv) hosts after bone marrow transplantation from C57BL/6-bgJ/bgJ or C57BL/6-bgJ/bgJ;Pgk-1a/Y mice. Electrophoretic pattern of hemoglobin was used as a marker of donor-type erythrocytes, giant granules of bgJ/bgJ mice as a marker of donor-type neutrophils, and A-type phosphoglycerate kinase-1 (PGK-1) as a marker of hematopoietic colonies produced by donor-derived progenitor cells. Repopulation of donor-type erythrocytes was significantly faster than that of donor-type neutrophils. Moreover, the extent of replacement was greater for erythroid progenitor cells than for nonerythroid progenitor cells. When nonirradiated WBB6F1-W/Wv mice with B-type PGK-1 received 10(5) bone marrow cells from C57BL/6-bgJ/bgJ;Pgk-1a donors, only approximately 20% replacement of erythroid progenitor cells gave rise to total reconstitution of erythrocytes. The present result suggests that normal multipotential stem cells may preferentially differentiate into erythroid lineage cells in anemic WBB6F1-W/Wv hosts and that normal erythroid progenitor cells may suppress the differentiation of erythroid progenitors of WBB6F1-W/Wv hosts.