The seminal vesicle of the adult Japanese monkey was observed by scanning electron microscopy. A number of spermatozoa are found scattered on the luminal surface. Some of them are normal in appearance, while others disintegrated. The epithelial cells bulging slightly into the lumen are devoid of cilia, but provided with diffusely distributed microvilli. The fracture surface reveals that the epithelium of the seminal vesicle consists of columnar epithelial cells with secretory activity and occasional basal cells, in accordance with the finding obtained by transmission electron microscope in other mammals. The most striking observation of this study is the occurrence of a number of macrophages lying on the epithelium of the seminal vesicle. They also are seen to engulf the disintegrated spermatozoa in bulk. The intraluminal macrophages observed may serve to dispose of spermatozoa which have migrated into the seminal vesicle for some unknown reason.