Nonsurgical intrahepatic shunts between the left portal vein and left hepatic vein were created in seven dogs with portal hypertension by means of a Grüntzig angioplasty catheter with a balloon diameter of 12 mm. This catheter was introduced coaxially through a stiff 18-French Teflon catheter (diameter, 6 mm) using transjugular approach. The procedure had to be repeated in weekly intervals up to five times (range, one to five times; average, 2.4 times) until an intrahepatic shunt remained permanently open. Animals with open intrahepatic shunts were followed for one month to one year. Immediately after production of an intrahepatic shunt, the portal pressure fell from 23.7 +/- 3.5 cm of water to 10.6 +/- 1.4 cm of water, and remained in that range during the follow-up period. Portal blood flow increased at the same time from 9.1 +/- 2.9 mL/min/kg to 15.1 +/- 3.5 mL/min/kg. One week after successful shunt production, a second, more gentle rise of portal flow began. It lasted several weeks and was accompanied angiographically by a corresponding increase in shunt diameter. At necropsy, a smooth transition between the intima of the portal and hepatic vein and the shunt was found. Histologically, the endothelialized shunt consisted of granulation tissue with collagen deposition at one month and of fibrous connective tissue three months and later.