CD34⁺/CD86⁺ cells cultured in SCF plus GM-CSF acquire the morphology and phagocytic properties of macrophages. Cytospins were prepared after 9 days of culture in the presence of SCF and GM-CSF, followed by Wright-Giemsa staining and microscopic analysis. CD34⁺/CD86⁻precursors gave origin predominantly to granulocytes, in addition to a small number of monocytes and macrophages (A; 100× amplification using oil immersion). CD34⁺/CD86⁺precursors generated macrophages (B). In a phagocytosis assay, latex particles were internalized by 12% of CD34⁺/CD86⁻ cell progeny stimulated by SCF plus GM-CSF (C) compared with 61% of CD34⁺/CD86⁺ cell progeny stimulated by SCF plus GM-CSF (D).