Estrogen receptor (ER)alpha and ERbeta mRNAs levels decreased with clinical stage, myometrial invasion and dedifferentiation. On the other hand, ERRalpha mRNA levels and histoscores increased with clinical stage and myometrial invasion, regardless of dedifferentiation. ERRalpha can bind to the steroid receptor coactivator family without any ligands, and drive transcription activity of the target genes. The competitive interaction of ERRalpha/ER expression associated with the use of common cofactors during loosing estrogen dependency might cause their expression manner. The up-regulation of ERRalpha might be related to tumor growth and advancement in uterine endometrial cancers. It is speculated that ERRalpha is a candidate for prognostic factors in uterine endometrial cancer, although ERRs are not directly related to growth of uterine endometrial cancer.