Eighteen healthy dogs were divided into three equal groups. All dogs were evaluated at the beginning of the experiment with complete physical examination, complete blood count, serum alanine aminotransferase, serum alkaline phosphatase, serum bilirubin, serum albumin, sulfobromophthalein. excretion test, ammonia tolerance test, glucagon response test, portal and intraparenchymal pressures, operative mesenteric portography, and histologic assessment of hepatic tissue. The left hepatic vein was ligated in the chronic and acute dogs. The dogs had a ligature placed loosely around the left hepatic vein. Acute and control dogs were evaluated 24 hours postoperatively with the hematologic and biochemical tests listed above. Acute dogs were evaluated with portal and intraparenchymal pressure, operative mesenteric portography and histologic evaluation of hepatic tissue at 48 hours postoperatively. Chronic and control dogs were evaluated at 4 weeks postoperatively with all of the tests listed above. The results of all tests performed supported a transient hepatic congestion which resolved bv the fourth postoperative week. No longstanding effect on hepatic function was found. The conclusion of this experiment was that, in normal dogs, left hepatic vein ligation does not cause severe or permanent liver damage. These findings support a clinical trial of this procedure in patients with patent ductus venosus. / Master of Science