Background and study aim: The prognosis of gallbladder cancer (GBC) is poor because it is typically diagnosed at an advanced stage and cannot be surgically treated. Moreover, even with advanced cancer, it is difficult to distinguish between malignant and benign disease. Therefore, pathological examination is indispensable for an appropriate diagnosis before surgery. Furthermore, a majority of tumors are diffusely infiltrating (flat-type). The diagnostic performance of various modalities is low for the flat-type GBC. We believe that cytology of gallbladder lavage-fluid (CGLF) contributes to definitive diagnosis and endoscopic doublecontrast cholangiography (EDCC) aids in the discovery in the infiltrating (flat-type) GBC. This study aimed to evaluate the efficacy of EDCC and CGLF by endoscopic transpapillary gallbladder drainage. Patients and methods: Between January 2005 and December 2011, 251 patients [men, 111; women, 140; mean age, 67 years (range 40-90 years)] suspected of GBC (an elevated lesion, thickening of the gallbladder wall, or gallbladder debris), were examined by EDCC and CGLF to confirm the diagnoses. Results: Of the 251 patients, 130 were diagnosed with benign disease on the basis of the results of follow-up examinations conducted for at least one year. Of the patients whose tissues were subjected to histopathological examination after surgery, 30 and 91 had GBC and benign gallbladder disease, respectively. The diagnoses of the 91 patients with benign disease included 62 with chronic cholecystitis, 11 with adenomyomatosis, 3 with hyperplasia, 3 with dysplasia, 11 with polyps, and 1 with xanthogranuloma cholecystitis. Of the 30 patients, 15 (50.0%) had earlystage GBC (pT1a, n = 11; pT1b, n = 4). The diagnostic accuracy of EDCC and CGLF was 87.3% and 96.4%, respectively. Of the 15 early-stage GBC, 9 (60.0%) were flat-type GBC. Conclusions: CGLF and EDCC using ETGD proved to be effective techniques for cytological diagnosis of GBC and were suitable for diagnostic imaging of infiltrating (flat-type) GBC. These techniques enhance surgical treatment and thus improve the prognosis of GBC.