The first scanning electron micrograph of erythrocytes seems to be that of PEASE and HAYES published in 1966. More advanced and detailed studies were made by CLARKE and SALSBURY (1967) and CLARKE (1967, see also CLARKE, SALSBURY and ROWLAND, 1968). These authors observed under the scanning electron microscope not only normal human erythrocytes but also pathological forms, e. g., red cells showing patchy denudation of the cell membrane after splenectomy, target cells and other irregular forms in thalassemia major, and typical deformities in sickle cell anemia, hereditary elliptocytosis and other hematological diseases.The present paper attempts a methodological analysis for the application of scanning electron microscopy to hematology with special reference to the osmotic effects of fixation, which has been performed by none of the previous authors as far as is known. It further aims to describe the detailed surface structure of normal human erythrocytes and their changes in some pathological conditions such as elliptocytosis, spherocytosis and aplastic anemia.