The purpose of this study was to evaluate change in the portal systemic pressure gradient (PSPG) following balloon-occluded retrograde transvenous obliteration (BRTO) and the aggravation of esophageal varices. The PSPG was monitored before and after BRTO in 19 patients. PSPG changes were obtained by subtracting the PSPG before BRTO from that after BRTO. The development of outflow vessels (e.g., left inferior phrenic vein) was classified into two grades: Grade 1, BRTO alone; and Grade 2, coil embolization plus BRTO. After confirming demonstration of the whole gastric varices on angiography and computed tomography, BRTO was conducted using a 5% ethanolamine-iopamidol mixture. Endoscopy was performed to evaluate gastric and esophageal varices before, within 1 month, and 3-6 months after BRTO. Eradication of gastric varices was obtained in all patients and aggravation of esophageal varices was seen in 11 patients. The PSPG was significantly elevated by BRTO (p=0.0362). The PSPG was significantly elevated in patients with Grade 2 compared with those with Grade 1 (7.7+/-3.7 vs. 3.3+/-4.3 mmHg, respectively; p=0.0314) and in those with esophageal varices before treatment compared with those without (7.4+/-4.0 vs. 3.2+/-3.9 mmHg, respectively; p=0.0482). The cumulative aggravation rate of esophageal varices was significantly higher in 11 patients with a PSPG elevation>5 mmHg than in 8 patients with one of <or=5 mmHg (p=0.0105). In conclusion, BRTO induced a significant elevation in PSPG, with the degree of elevation influencing the aggravation of esophageal varices following BRTO.