We report 5 polypoid high-grade neuroendocrine carcinomas of the uterus, 2 small cell carcinomas of the endometrium, and 3 large cell neuroendocrine carcinomas, 2 from the cervix and 1 from the endometrium. The 2 small cell carcinomas of the endometrium arose from and were confined to endometrial polyps, one of which also showed foci of endometrioid adenocarcinoma. The myometrium was free of tumor, despite extensive sampling. The 3 large cell neuroendocrine carcinomas, 2 from the cervix and 1 from the endometrium, were polypoid but did not originate in polyps. Two of these tumors infiltrated myometrium, and one did not. The age of the 5 patients ranged from 25 to 66 years (mean age, 43 years). Four patients presented with vaginal bleeding. One pregnant woman had the largest polypoid tumor discovered during a routine gynecologic examination. Tumor sizes ranged from 2.7 to 10 cm. All 5 patients were treated by radical hysterectomy and 4 received adjuvant chemotherapy. Only 2 patient had pelvic lymph node metastasis. All patients are alive and disease-free from 9 months to 7 years after treatment (mean survival, 47 months). All 5 tumors labeled with chromogranin and synaptophysin and 4 with CD56. Two small cell carcinomas and 2 large cell neuroendocrine carcinomas accumulated p53 protein. Two small cell carcinomas and 2 large cell neuroendocrine carcinomas expressed p16. Our findings suggest that stage of disease and a polypoid gross feature are the best predictors for outcome in small cell carcinomas and large cell neuroendocrine carcinomas of the uterus.