The fine structure and subepithelial capillaries of the main excretory duct epithelium (MEDE) of the submandibular gland in the Japanese monkey, Macaca fuscata were investigated by light, scanning, and transmission electron microscopy. Capillaries found beneath the MEDE were all fenestrated ones. Some of them had elevated endothelium known as pored domes. The capillary density (number of capillaries per 200 μm length of MEDE) was 6.05 ± 1.36, and the number of fenestrae per 10 μm length of available endothelium was 11.62 ± 3.82. The MEDE was pseudostratified, and consisted of four cell types: Type I and II, which were columnar cells without basal infoldings, basal and goblet cells. The most characteristic feature was the presence of well-developed lateral interdigitations between Type I and II cells. © 1993 Wiley-Liss, Inc.