The vascular anatomy of the skin and fascia of the leg were studied in 20 cadaver legs that were injected and dissected under magnification to identify the origin, course, and distribution of vessels from the subfascial level to the skin. In addition to the longitudinally oriented fasciocutaneous arteries and the musculocutaneous perforators, the study demonstrated a third and important system of blood supply: the septocutaneous vessels. These vessels arise directly from the posterior tibial, anterior tibial, and peroneal arteries, run along the intermuscular septum, pierce the crural fascia, and ramify radially in the subcutaneous tissue superficial to the fascia. Longitudinally oriented anastomotic arcades are formed along the leg between branches of adjacent septocutaneous vessels. Each septocutaneous vessel has one or two venae comitantes. Selected methylene blue injections of the septocutaneous vessels revealed rich staining of the superficial surface of the fascia, the subcutaneous tissue, and distinct longitudinally oriented skin territories. There was no injection of dye in the deep surface of the fascia. It is felt that the septocutaneous vessels constitute an important source of skin circulation in the leg and form the basis for various fasciocutaneous flaps that have useful clinical applications.