Overexpression and mutation of p53 in 46 primary endometrial carcinomas were determined comparatively with the status for estrogen receptor (ER) and progesterone receptor (PR). Immunohistochemically p53 overexpression was found in 9 of 46 cases (20%), while eight kinds of mutations in that gene were detected in 7 of 46 endometrial carcinomas (15%), using polymerase chain reaction single-strand conformation polymorphism and subsequently direct sequencing method. Six of nine cases with p53 overexpression showed p53 mutation. All eight mutations showed single substitutions, and three cases in exon 4, one in exon 5, two in exon 6, and two in exon 7 were found. The cases with the p53 overexpression were significantly inversely related to that of ER or PR staining. Most endometrial carcinoma with p53 overexpression and/or mutation had a relatively poor prognosis and showed no reactivities of ER or PR.