Saphenous veins are used extensively to replace stenotic coronary arteries. However, the contractile and biochemical adaptations of grafted veins are unknown. The three purposes of this work were to characterize the contractile properties of grafted veins, to determine whether altered contractile characteristics were associated with quantitative changes in actin, myosin and collagen, and to determine which changes were associated with the surgical procedure and which with placement in the arterial circulation. Canine saphenous veins were removed and returned to their original location (venous autograft), while others were used to replace a segment of femoral artery (arterial graft). The grafts were removed 1, 4, and 8 weeks later and compared with the contralateral saphenous vein. Both graft types exhibited an increase in sensitivity to norepinephrine but not to potassium chloride. The venous autograft exhibited a reversible reduction in myosin content and in maximum contractile response (force/cross-sectional area) to potassium chloride and norepinephrine. In contrast, the arterial graft exhibited increased wall thickness and content of all measured proteins and decreased maximum contractile response. The latter occurred even though there was an increase in the net production of actin and myosin. Expressing the maximum contractile response in terms of the myosin content did not normalize the contractile response. These results suggest that, except for the elevated sensitivity to norepinephrine, the vein is capable of recovering from the effects of surgery within 8 weeks; however, placement of the vein in the arterial circulation delays this recovery and initiates a hypertrophic response that includes an attenuation of contractile function.