Venous flaps may become more versatile in reconstruction and offer different opportunities to reconstructive surgeons if the mechanisms of their viability is clarified. In this study, axial pattern flank flaps in rabbits were converted into venous flaps by dividing the cutaneous pedicles and ligating the artery. Fluorescein and radioactive tracer studies were performed to elucidate the mechanisms of possible circulation. It is hypothesized that the venous flaps do not have a capillary circulation, but veins transport the fluid out, which is drawn into the capillaries from the interstitium, and that the nutrients and oxygen for flap viability diffuse from the wound bed. Venous drainage plays an important role by draining the metabolites away until revascularization offers a more direct supply.