Vascular remodeling induced in rat limb by arteriovenous (AV) shunting was investigated by evaluating changes in vascular diameter and cell morphology. In Wistar rats, a vein graft was implanted in situ in the hind limb. Flow-rate in the grafted vein was assessed by measuring flow in the common femoral artery using an ultrasonic flowmeter. Nuclei and actin filaments of the venous wall were stained with propidium iodine and phalloidine-FITC, and the samples were observed using confocal laser microscopy. The grafted veins became circular in cross-section with increase in diameter during two weeks after AV shunting. Owing to the increase in diameter, the estimated wall shear stress was not increased so much as the flow-rate. The confocal laser microscopic observation showed that endothelial cells (ECs) and smooth muscle cells (SMCs) in the grafted veins were either aligned well (2 out of 8 samples), or ECs were denudated and SMCs were disrupted (in 6 out of 8 samples). The cell density of ECs was unchanged from the control level. In conclusion, the grafted vein was remodeled with morphological changes in ECs and SMCs during 2 weeks after AV shunting.