Primary squamous cell carcinoma of the endometrium is exceedingly rare. To be accepted as a primary carcinoma of the endometrium, the tumor must satisfy the criteria estalished by Fluhmann: There must be; 1) no coexisting endometrial adenocarcinoma, 2) no connection between the endometrial tumor and the squamous epithelium of the cervix, and 3) no squamous cell carcinoma of the cervix. We recently experienced a case of primary squamous cell carcinoma of the endometrium covering the submucosal leiomyoma in a 68-year-old female patient. On gross examination a submucosal leiomyoma covered by an irregular, dirty endometrium was found. On histologic examination the endometrium covering the leiomyoma revealed invasive, well differentiated squamous cell carcinoma. The uterine cervix showed no evidence of malignancy. In situ PCR using a probe for HPV 16/18 was negative in the carcinoma tissue.