Objective To investigate the effects of the extent of regional lymph node dissection on the prognosis of patients with T4 gallbladder carcinoma. Methods The retrospective cohort study was conducted. The clinicopathological data of 64 patients with T4 gallbladder carcinoma who underwent radical cholecystectomy in the 4 medical centers between January 2013 and December 2016 were collected, including 31 in the Eastern Hepatobiliary Surgery Hospital of Naval Medical University, 16 in the First Affiliated Hospital of Xi′an Jiaotong University, 11 in the Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine and 6 in the Affiliated Hospital of North Sichuan Medical College. There were 27 males and 37 females, aged from 35 to 77 years, with a median age of 59 years. Sixty-four patients underwent radical cholecystectomy and regional lymph node dissection. According to the extent of intraoperative lymph node dissection, 25 patients (13 in the Eastern Hepatobiliary Surgery Hospital of Naval Medical University, 6 in the First Affiliated Hospital of Xi′an Jiaotong University, 4 in the Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine and 2 in the Affiliated Hospital of North Sichuan Medical College) whose extent of lymph node dissection involved lymph nodes next to cystic duct, hepatoduodenal ligament, back of head of pancreas, next to common hepatic artery and celiac trunk were allocated into the extended dissection group, 39 patients (18 in the Eastern Hepatobiliary Surgery Hospital of Naval Medical University, 10 in the First Affiliated Hospital of Xi′an Jiaotong University, 7 in the Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine and 4 in the Affiliated Hospital of North Sichuan Medical College) whose extent of lymph node dissection involved lymph nodes next to cystic duct and hepatoduodenal ligament were allocated into the control group. Observation indicators: (1) postoperative complications; (2) follow-up and survival situations. Follow-up using outpatient examination and telephone interview was performed to detect postoperative overall survival up to January 2018. Measurement data with normal distribution were represented as Mean±SD, and comparison between groups was evaluated with the independent-sample t test. Count data were represented as absolute number or percentage, and comparison between groups was analyzed using the chi-square test and Fisher exact probability. The survival curve was drawn using the Kaplan-Meier method, and the comparison of survival rates was done by the Log-rank test. Results (1) Postoperative complications: 64 patients with T4 gallbladder carcinoma underwent successful radical cholecystectomy and regional lymph node dissection, without intraoperative death. Twelve patients had different degrees of postoperative complications. Four of 7 patients undergoing extended radical cholecystectomy had postoperative complications. Twenty-five patients in the extended dissection group were cured by conservative treatment, including 4 with intraperitoneal infection and 2 with pancreatic leakage, with a complication incidence of 24.0%(6/25). Thirty-nine patients in the control group were cured by conservative treatment, including 5 with intraperitoneal infection and 1 with gastric retention, with a complication incidence of 15.4%(6/39). There was no statistically significant difference in the complication incidence between the two groups (χ2=0.284, P>0.05). (2) Follow-up and survival situations: 64 patients were followed up for 1-60 months. The postoperative overall median survival time was 11 months. The postoperative median survival time, 1-, 3- and 5-year cumulative survival rates were respectively 18 months, 80%, 16%, 9% in the extended dissection group and 8 months, 21%, 4%, 0 in the control group, with a statistically significant difference in the prognosis between the two groups (χ2=14.744, P<0.05). Conclusions On the premise of practiced surgical skill, extended regional lymph node dissection cannot increase incidence of surgical complication in patients with T4 gallbladder carcinoma after radical resection. Actively extending lymph node dissection up to near common hepatic artery, peri-celiac trunk and back of head of pancreas can improve long-term survival and prognosis. Key words: Biliary tract neoplasms; Gallbladder carcinoma, stage T4; Radical resection; Regional lymph node dissection; Multi-center; Retrospective research