Primary clear cell adenocarcinoma of uterine cervix is rare and cytomorphology in the vaginal smear have not been previously described in Korean literatures. The cytologic characteristics of clear cell adenocarcinoma of the uterine cervix include : malignant cells with abundant, finely vacuolated cytoplasm ; hobnail appearance ; and distinctive basement membrane-like hyaline materials within cellular aggregates. A 36-year-old woman presented with vaginal bleeding. Cytologic examination of vaginal smear and histopathologic examination of a radical hysterectomy specimen allowed the diagnosis of hemorrhagic tumor in the uterine cervix as a clear cell adenocarcinoma. Cytologic findings were very characteristic. The tumor cells had abundant, pale, finely vacuolated cytoplasm with indistinct cytoplasmic membrane. The nuclei were round to oval with finely dispersed chromatin. Extracellular basement membrane-like hyaline substance, which stained a light green color in Papanicolaou's preparation, was frequently observed within the cancer cell clusters.