The microvascular architecture of the mouse testis and excurrent duct system was examined by a casting method with the aid of scanning electron microscopy and by sectioning techniques for light and transmission electron microscopy. Two fundamental types of peritubular capillary arrangements were noted in relation to the tubules. The first type most typically appeared in the testis. In this type, peritubular capillaries interconnected intertubular blood vessels to form a rope-ladder-like structure. The length of the individual peritubular capillaries was short, and a number of the capillaries encircled each tubule. Adjacent tubules shared a single layer of capillaries. The vascular organization of the ductuli efferentes and of the middle segment of the epididymis was also of this type, but the number of peritubular capillaries was much fewer compared with that of the testis. In the second type, the peritubular capillaries formed a network encircling each tubule in its subepithelial layer. The capillary organization in the initial and terminal segments of the epididymis and the ductus deferens belonged to the second type. In the distal part of the ductus deferens, a prominent venous plexus was formed in the most peripheral subepithelial layer.