Background/Aims: The ballooning time in endoscopic papillary large balloon dilation (EPLBD) remains controversial. The aim of this study was to evaluate the significance of the ballooning time comparing an immediate balloon deflation method with a conventional ballooning time of > 45 seconds. Methods: Between January 2010 and December 2010, 126 patients with bile duct stones treated with EPLBD and endoscopic sphincterotomy were divided according to the ballooning time: the immediate deflation group (n=56) and the conventional inflation group (ballooning time 45s to < 60s) (n=70). Results: The overall success rate and the success rate of the first attempt of ERCP (endoscopic retrograde cholangio-pancreatography) were 96.4% (54/56) and 80.4% (45/56) in the immediate group and 97.1% (68/70) and 77.1% (54/70) in the conventional inflation group. There were no statistically significant differences in the overall success and the first attempt of ERCP success rate (p=0.99, p=0.66). The frequency of mechanical lithotripsy was 0% in the immediate deflation group and 7.1% in the conventional inflation group (p=0.065). Complications occurred in 3.6% (2/56) patients in the immediate deflation group and 8.6% (4/70) patients in the conventional inflation group (p=0.298). Conclusions: The ballooning time in EPLBD does not affect the outcomes of the treatment for bile duct stones. And the feasibility of the immediate deflation method in EPLBD is acceptable.