On microscopic examination of a cervical carcinoid removed from a 29-year-old woman, foci of endocervical adenocarcinoma in situ (AIS) and severe squamous dysplasia were present immediately adjacent to the invasive carcinoid tumor. Cells of the carcinoid tumor contained abundant intracytoplasmic argyrophilic granules and numerous neurosecretory granules (NSG) on ultrastructural study. Neoplastic cells of the endocervical AIS were devoid of argyrophilic granules and contained no NSGs. The present neoplastic process appeared similar to cases of a "mixed" type neoplasm composed of a carcinoid tumor and an adenocarcinoma, which have been reported from several areas of the body but only once previously from the cervix. The possible mechanisms accounting for such an unusual neoplastic process are discussed.