The argyrophilic nucleolar organizer regions (AgNOR) are silver stained granules that are thought to correlate with cell proliferation activity. Two AgNOR counting methods: the mean AgNOR count (mAgNOR, the mean number of AgNOR granules in 100 cells) and the AgNOR proliferative index (pAgNOR, the percentage of cells exhibiting five or more AgNOR granules per nuclei) have been proposed. In this study, the two counting methods were applied to 58 cases of normal uterine corpus and uterine corpus tumors and were compared with the Ki-67 labeling index (Ki-67 LI) using MIB-1 monoclonal antibody and other histopathological criteria. Notable differences in the number of AgNOR and the Ki-67 LI were observed between benign and malignant smooth muscle tissue. Histopathologic features are well correlated to the proliferative activity of tumors. Although the most reliable method of predicting malignant potential cannot be determined, the methods outlined by this study are thought to be highly useful in assessing proliferative activities.