It has been reported that overexpression of HER-2/neu occurs in one third of breast and ovarian cancers and that overexpression is associated with poor prognosis. A polyclonal antibedy against HER-2/ neu oncoprotein was used to assess immunohistachemically the level of HER-2/neu expression in normal and malignant endometrial carcinoma. In 8 normal endometrial samples light to moderate(0- +2) staining for HER-2/neu was seen in the giands, and there was no variation in intensity of staining during the menstrual cycle, Among 15 endometrial adenocarcinomas. three(20%) were found to have heavier staiaing (+3) for HER-2/neu than was seen in normal endometrium. High expression of HER-2/neu was found in 50%(1/2) of patients with metastatic disease(stages III or more) compared with 15%(2/13) of patients with disease confined to the uterus(stage I). Survival of the 3 patients with high HER-2/neu expression was significantly worse than that of the 1.2 patients with normal HER-2/neu expression. (Median survival: 49. I vs 28. 7 months (p=0.0348)) Further studies are needed to determine the significance of HER-2/ neu overexpression in endometrial cancer.