Cyclins are the regulatory subunits of cyclin-dependent kinase and play an important role in cell proliferation. Many tumors, such as colon, breast and gastric carcinomas are known to be involved in the deregulation or amplification of cyclins, especially cyclin E, which involves the restriction point of G1-S transition. We investigated the expression of cyclin E in benign and malignant epithelial tumors of the gallbladder and compared the results with the activity of cell proliferation by the Ki67 antigen using immunohistochemical staining. Cyclin E was expressed in the adenocarcinoma tissue in 33.3% of patients (4 out of 12 cases), whereas only one out of 8 cases of adenoma expressed cyclin E (12.5%). There was a correlation between cyclin E expression and the Ki67 labeling index. These results suggest that the high expression of cyclin E in adenocarcinoma of the gallbladder is related to a high rate of cell proliferation.