Adenoma malignum is an extremely well-differentiated variant of cervical adenocarcinoma in which the cells composing the tumor lack the typical cytological features of malignancy. The prognosis of this rare tumor is poor in spite of high degree of differentiation. The cytologic characteristics are extremely bland so frequently make a confusion of adenoma mailgnum with endocervical glandular hyperplasia. We report a case of adenoma malignum in a 35-year-old woman who complained of mucoid vaginal discharge and vaginal bleeding. The cervicovaginal smear showed endocervical cells exhibiting a spectrum of atypical chances. The cells were arranged in multilayered strips and monolayered sheets. Individual cells ranged from cuboidal to columnar; typically the columnar cells had abundant lacy or vacuolated cytoplasm. The smear showed the majority of only atypical cells and small numbers of frankly malignant cells.