Adenomyomatosis of the gallbladder has not been considered to have malignant potential, but gross features of adenomyomatosis are sometimes encountered in gallbladders resected under a diagnosis of gallbladder carcinoma. The purpose of this study was to determine the clinicopathologic features and survival rates in cases of gallbladder cancer with gross features of adenomyomatosis. The study subjects were 97 surgically treated gallbladder carcinoma patients. Only gallbladder showing typical gross features of adenomyomatosis was judged as adenomyomatosis-positive gallbladder cancer. In terms of gross findings, 25 cases (25.8%) were classified as adenomyomatosis-positive. The status of adenomyomatosis was significantly associated with the T stage (P = 0.0004), lymph node (LN) metastasis (P < 0.0001), distant metastasis (P = 0.008), and stage (P = 0.0005). In the adenomyomatosis-positive group, 16 of the 25 cases (64.0%) were classified as segmental type and 9 cases (36.0%) were classified as fundal type. No diffuse-type cases were present in this series. The status of adenomyomatosis correlated significantly with survival (P = 0.0007). However, the multivariate analysis of significant variables identified from the univariate analysis identified only T stage (P = 0.0178) and LN metastasis (P = 0.0048) as independent prognostic factors. Subset analysis with T stage according to the status of adenomyomatosis showed no significant impact on survival. These results indicate that adenomyomatosis-positive gallbladder cancer is more often diagnosed clinically in the advanced stages. Since preceding adenomyomatosis may prevent the early detection of gallbladder cancer, the usefulness of preventive cholecystectomy in cases of asymptomatic adenomyomatosis should be considered.