Human peripheral blood may be an alternative to bone marrow as a source of cells for hemopoietic engraftment. The ability to collect large numbers of circulating granulocyte‐macrophage progenitors provides support for this contention. In the present study of cells from normal granulocyte donors, the cell concentrates obtained by cytapheresis were shown to contain even greater numbers of primitive erythroid precursors (153–956 [median 647] per 106 mononuclear cells) than would be predicted from the peripheral blood mononuclear cell counts. Moreover, the number of primitive erythroid precursors harvested correlated significantly with the number of granulocyte‐macrophage progenitors obtained and with the total lymphocyte collection. These observations further substantiate the validity of transplanting peripheral blood as hemopoietic tissue.