The arterial blood supply of the distal radioulnar joint was investigated in 35 upper extremities taken from 22 fresh cadavers (11 newborns and 11 adults using the India ink injection and tissue-clearing techniques according to Spalteholz). Microvasculature of the articular disk of the distal radioulnar joint was also performed in 35 articular disks taken from 22 fresh human cadavers, 11 newborn and 11 adults using the same technique. It was found that the general blood supply to the joint is received mainly from the palmar and dorsal branches of the anterior interosseous artery. These branches, after dividing at the proximal border of the pronator quadratus, arborize in a fanlike fashion around the joint and their small ramifications penetrate and vascularize the capsule and the articular disk from the palmar, dorsal, and medial sides. The terminal branches of the anterior interosseous artery reinforced by the posterior interosseous artery and a small branch of the ulnar artery give the direct peridiscal vessels to the palmar, medial, and dorsal margins of the articular disk, which arborize and anastomose with one another and form the terminal capillary networks that end at the peripheral segments of the disk in a series of terminal capillary loops, leaving the inner segments devoid of blood vessels. The posterior interosseous artery anastomoses at the distal part of the forearm with one of the terminal rami of the dorsal branch of the anterior interosseous artery and, in that way, contribute to the vascularization of the dorsal capsule of the distal radioulnar joint. The ulnar artery gives off a small branch that anastomoses with one of the terminal ramifications of the palmar branch of the anterior interosseous artery and contributes to the formation of a small arterial arch on the anteromedial side of the distal ulna, supplying the anteromedial capsule and the basistyloid area of the ulna. Both ulnar and radial arteries contribute to the vascularity of the joint through the collateral network of the palmar and dorsal carpal arches. In the articular disk, the major central portion of the disk is avascular and only its peripheral, palmar, medial, and dorsal margins are vascularized. The proportion of vascularized zone to avascular zone depends on the age of the subject and, in newborns, is approximately 33%. In adults, only 25% of the peripheral segments are vascularized.(ABSTRACT TRUNCATED AT 400 WORDS)