The electron microscopic changes in genetic and acquired disorders of granulocytes have been reviewed. In rare situations, such as the Chédiak-Higashi syndrome, there are bizarre giant lysosomes. In other conditions associated with abnormal phagocytic function, such as chronic granulomatous disease, there are no qualitative morphologic abnormalities. In chronic infection and in protein calorie malnutrition (kwashiorkor) granulocytes contain frequent Döhle bodies and cytoplasmic vacuolization. The development of new cytochemical methodology and the combination of electron microscopy with in vitro techniques offers the potential for further understanding of the relationship between cell structure and functional disorders of the granulocyte.