Cases (8) of microglandular hyperplasia arising in vaginal adenosis are presented. Five patients had taken oral contraceptives and a 6th was pregnant at the time the lesion was discovered; a history of prenatal exposure to diethylstilbestrol (DES) was present in 5 cases. It is important to differentiate microglandular hyperplasia, which is benign, from clear cell adenocarcinoma, which arises in a background of vaginal adenosis.