The blood supply to the lower extremity has been reviewed, and the concept of direct arterial or axial supply at the groin, fasciocutaneous perforators, and septocutaneous blood vessels in the lower leg has been outlined. The major myocutaneous and fasciocutaneous units in the lower extremity have been outlined and their applications described. All of the reconstructive flaps available are based on a clear understanding of the underlying blood supply. We have tried to look toward what might be multiple contributions of blood supply that may change flap design in an anatomic territory or alter the flap concept entirely. An example would be a myocutaneous flap and its overlying fasciocutaneous territory, or a flap based on a septocutaneous perforator. The plastic surgeon has truly benefited from more in-depth study of the lower extremity blood supply.