It is known that esophageal varices (EV) appear or aggravate after balloon-occluded retrograde transvenous obliteration (B-RTO) for gastric varices (GV) in some patients. The aim of this study was to investigate a relationship between the appearance or aggravation of EV after B-RTO and the degree of development of left gastric vein (LGV) estimated by endoscopic ultrasonography (EUS) performed before B-RTO in 20 patients. EV appeared or aggravated in 11 patients (55%). Among them, 5 patients (25%) had to be treated. Diameter of LGV correlated with the progress of EV after B-RTO. On the other hand, EV did not aggravate in 4 patients with developed LGV, which had no intramural perforating vein and flowed into extramural collateral vessels. Assessment of LGV by EUS is useful to predict the aggravation of EV after B-RTO.