Elemental X-ray microanalysis of normal peripheral blood neutrophils, lymphocytes, monocytes and platelets was carried out with a scanning electron microscope fitted with an X-ray analytical system. Each cell type was characterized by its own spectrum. Nucleus containing cells displayed a high phosphorus level, while platelets showed a low peak of this element. The elevated level of sulfur observed in platelets, neutrophils and monocytes may result from their cytoplasmic granules which contain sulfur-rich substances. The highest amount of calcium was detected in the platelets. The results indicate that X-ray microanalysis may be applied for the detection of the elemental content of blood cells.