A skin flap in the anterior abdominal wall of the S-D rat was designed so that it was supplied by the superficial epigastric branch of the femoral artery on the right side. Venous drainage was effected through one of five designs: (1) the superficial epigastric vein on the same side, (2) the lateral abdominal vein on the same side, (3) the lateral abdominal vein on the opposite side, (4) the superficial epigastric vein on the opposite side, or (5) a combination of the latter three. Seventy-seven rats were available for final analysis. The surviving percentage area of the flap was found to improve with increased venous drainage and when the arterial blood had to traverse the flap to reach the diagonally situated draining vein. The use of venae commitante as the draining vein is not satisfactory.