The porto-systemic collaterals were studied in rats 14 weeks after making a 1.2-mm stenosis of the portal vein. A prominent shunt from the coronary-lienal vein to the left suprarenal and renal veins was found angiographically in all rats with portal vein stenosis. This shunt was also visible following Indian ink injection in normal controls, and represents dilatation of pre-existing communications and absence of development of new vascular channels. Dilated perioesophageal veins were not detected angiographically but were a constant finding in stenosed rats following Indian ink injection. They were not observed in normal controls. The present findings are discussed in relation to previously reported collaterals in rats with cirrhosis of the liver.