BACKGROUND AND OBJECTIVES Reflux is one of the most common sequela after proximal gastrectomy (PG). The aim of this study was to find a predicting factor related to the character of esophageal reflux after PG. METHODS Wireless ambulatory 24-hr pH monitoring (for acid reflux, AR) and diisopropyliminodiacetic acid hepatobiliary scan (for bile reflux, BR) were performed on 24 patients who had reflux symptoms after PG with esophagogastrostomy from July 2008 to March 2009. Endoscopic examination was done and the length of remnant stomach (LoRS) was measure by postoperative UGI series. RESULTS Eleven patients (45.8%) had only BR, 7 (29.2%) had AR only, Two patients (8.3%) had both acid and BR, and 3 (12.5%) had neither. The LoRS along greater curvature was significantly shorter in patients with only BR (16.11 +/- 2.87 cm) than in patients with only AR (23.69 +/- 6.15 cm, P = 0.003). Severity of symptoms or esophagitis was not significantly correlated with the content of acid or BR. CONCLUSION Reflux symptom after PG is caused by either bile or acid rather than both. Character of reflux was related to the LoRS.