Effect of somatostatin analogue (octreotide) on blood flow to endocrine tumors metastatic to the liver: angiographic evaluation. The effect of an octapeptide analogue of somatostatin, octreotide, on tumor blood flow was evaluated with angiography in eight patients with hepatic endocrine tumors; one patient had primary intrahepatic gastrinoma, two patients had hepatic metastases from gastrinomas, two patients had VIPomas (vasoactive intestinal polypeptide-secreting tumor), and three patients had carcinoid tumors. Octreotide caused a marked decrease in tumor blood flow in two patients with gastrinomas and two with VIPomas. One patient could not be evaluated due to the lack of a tumor blush on a control angiogram. In patients with carcinoid tumors, octreotide caused a slight reduction in blood flow through the tumors in two patients, while there was no change in one patient. Octreotide markedly decreased gastrin and gastric acid secretion in two of three patients with gastrinomas, lowered VIP and stopped the diarrhea in patients with VIPomas, and controlled symptoms in two of three patients with carcinoid tumors. The vasoactive effect of octreotide on hepatic endocrine tumors may be a direct action on tumor blood supply or secondary to inhibition of the endocrine tumor cell secretion and consequent decreased blood flow. 