To assist in the interpretation of buffy coat smears from leukopenic patients, we determined the composition of the buffy coat of the blood of normal volunteers. Leukocytes were concentrated by centrifugation in microhematocrit tubes. Stained smears of these cells showed minor differences in the proportions of neutrophils, lymphocytes, and monocytes when compared to unconcentrated peripheral blood. Granulocytes of greater immaturity than the metamyelocyte were not encountered, and their presence should suggest the possibility of marrow dysfunction. Occasional young monocytoid cells and "stimulated" lymphocytes were seen.