To investigate the properties of endocytosis in the marginal cells of stria vascularis (SV), we perfused cationized ferritin (CF), an endocytosis tracer, into the cochlear duct. After five minutes to two hours of endolymphatic perfusion, the tissues were fixed and the distribution of CF was observed by transmission electron microscopy. CF was endocytosed by the marginal cells. CF-loaded vesicles were represented mainly by coated vesicles. The time-course of endocytosis was as follows. After five minutes perfusion, CF was distributed over the surface of the apical membrane and CF-loaded vesicles were seen very close to the apical membrane. After 30 minutes perfusion, a number of CF-loaded small endosomes and CF-loaded large vacuolar endosomes were observed at the supranuclear region. After one hour and two hours perfusion, CF was transferred to the multivesicular body. After two hours perfusion, acid phosphatase (ACPase) activity, a marker of lysosomes, was investigated. CF was not transferred to lysosomes until after two hours, because ACPase activity was not seen in CF-loaded vesicles. In this paper, we discuss the basic endocytosis properties of marginal cells.