The thin-walled structure of veins leads them to stay collapsed during anastomoses, thereby the incidence of technical failures is more common than arterial anastomoses. In order to overcome this problem, we are introducing the use of viscoelastic material based on our experience on rats. Six rats were used in order to study the technical feasibility of the viscoelastic material during microsurgical vein anastomosis. End-to-end anastomoses were performed on rat jugular veins using 0.5-1 mL of the viscoelastic medium applied to the ends of the veins and surgical field under X30 operating microscope magnification. Then 1.8% (n:3) and 3.0% (n:3) hyaluronic acid was used as a viscous medium in order to keep the vein lumens open during anastomosis. In conclusion, we have found that 3.0% hyaluronic acid viscoelastic medium facilitates microvenous anastomosis in rat. Studies involving human practice are needed for further evaluation of this technical refinement.