On the basis of the functional characteristics of microcirculation in tumor tissue, the clinical results of angiotensin II-induced hypertension chemotherapy (IHC) have been reported. The present paper deals with the results of measurement of blood flow in human tumors transplanted into athymic rodents using the electrolytic hydrogen clearance method. When the mean arterial blood pressure was elevated to 140-150 mmHg by the continuous infusion of angiotensin II, the increase of blood flow was 30.4 +/- 4.7 ml/min/100g in H-111 human gastric carcinoma (the mean increase rate being 14.4 times that in the normotensive state), 15.6 +/- 2.6(X 3.0) in NS-8 gastric carcinoma and 11.0 +/- 2.9 (X 2.9) in TE-8 esophageal carcinoma, respectively. These results confirmed that blood flow remarkably increased not only in animal tumors but also in human tumors under the induced hypertension caused by angiotensin II. On dynamic CT under hypertension, enhancement of the delivery of contrast medium to the tumor area was also shown clinically, according to the increase in CT numbers in the same ROIs in a normotensive state.