Glycogen of normal human blood leukocytes was studied in cell suspensions containing chiefly neutrophiles. In electron micrographs of neutrophiles stained with lead the glycogen particles appear to be relatively uniform with a diameter of 20 mmu. At high magnification the 20 mmu particle appears to be composed of at least eight subunits. Leukocyte glycogen released by lysis or homogenization sediments as a single peak of high molecular weight material. The great majority of the cell glycogen can be accounted for in the large molecular weight material. The large molecular weight material is degraded to small fragments by alpha-amylase and partially degraded by beta-amylase. Purification of cell glycogen by alkali extraction and ethanol precipitation produces a relatively uniform particle smaller than the original native macromolecule. Native glycogen was prepared in pure form by a sucrose density gradient technique and its purity demonstrated by its susceptibility to purified alpha-amylase and by analytical ultracentrifugation.