We report one case of hepatic encephalopathy following the administration of a somatostatin analogue (lanreotide) in a patient with a pancreatic endocrine tumor and liver metastases. Hepatic insufficiency was absent. The diagnosis of hepatic encephalopathy relied upon a positive re-challenge test, elevated veinous ammonemia, suggestive findings on electroencephalogram and lack of recurrence after lanreotide discontinuation. Encephalopathy was thought to be due to a significant decrease in hepatic blood flow caused by lanreotide; an associated thrombosis of the portal vein may have played a facilitating role.