Periodic acid methenamine silver staining has been used for proof of the existence of carbohydrates in both paraffin and resin embedded tissues. The staining was applied to delineate macrophages that have been well known as cells of mononuclear phagocyte system by stainable nature for lysosomes, and it is found to be usefu1 method for detection of macrophage. Fetal macrophage, which is often observed in placental villi, is called the highly vacuolated cell. Vacuoles in the cytoplasm seem to be empty with light mieroscopic staining, but it is clarified that they contain a ful1 amount of carbohydrate. The present result leads us to the necessity of reconsidering the functional aspect of fetal macrophage.