To evaluate the significance of mitotic activity and apoptosis in the differential diagnosis of endocervical glandular lesions, we examined the frequency of mitoses and apoptosis in 89 endocervical glandular lesions from 78 patients, which consisted of benign reactive changes (7 cases), lobular or diffuse laminar endocervical glandular hyperplasia (4), microglandular hyperplasia (3), tunnel clusters (7), nabothian cysts (2), mesonephric remnants (3), tubal metaplasia (3), endocervical glandular dysplasias (including atypical tubal metaplasia) (EGD) (7), adenocarcinoma in situ (AIS) (31), microinvasive adenocarcinoma (7), frankly invasive adenocarcinoma (12), and minimal deviation adenocarcinoma (3). Mitotic index (MI; mitotic figures per 1000 cells) was significantly higher in AIS, microinvasive adenocarcinoma, and frankly invasive adenocarcinoma than any other lesions examined. Microinvasive adenocarcinoma showed the highest MI. Apoptosis was detected consistently and frequently in AIS, microinvasive adenocarcinoma, and frankly invasive adenocarcinoma. AIS showed the highest apoptotic index (AI; apoptoses per 1000 cells). Frequent apoptotic bodies and mitotic figures are a common feature of endocervical glandular malignancies (except for minimal deviation adenocarcinoma) and are an important feature that can facilitate their differentiation from benign and borderline lesions. High MI in microinvasive adenocarcinoma might aid the distinction of microinvasive adenocarcinoma from AIS. Although both MI and AI of EGD were between those of benign reactive changes and of AIS, MI and AI alone are not sufficient to differentiate EGD from benign reactive changes. MI and AI are not helpful in the differential diagnosis between minimal deviation adenocarcinoma and its benign mimics.