In spite of all the successful advances in microvascular surgery, the use of arterial graft is still a subject of controversy. To elucidate the advantages and indications of arterial grafts in microsurgery, venous and arterial grafts were transplanted to the femoral artery of the rat, and the former was investigated histopathologically one, two, three, four, six and eight weeks, and the latter one, two, three and four weeks after transplantation. As the results, intimal thickening was noted in neither of the two grafts. In the venous grafts, endotherial cells were almost separated two weeks after transplantation, and the media showed fibrous replacement. In contrast, the intima remained unchanged and the media maintained its layers of smooth muscle cells in the arterial grafts. The arterial grafts showed little post-transplantation change and maintained their pre-transplantation structure, retaining contracting and dilating function. Based on these results, arterial grafts might be applied clinically in microsurgery.