An experimental nude mouse system where human endometrial carcinomas of different histologic grade and steroid receptor characteristics can be grown and maintained under defined hormonal milieu by serial transplantation has been developed. Biologically and clinically important information on the role of steroid receptors in eliciting hormonal responses in these tumors has been obtained using this model. These results form the basis for designing and testing various treatment strategies for endometrial carcinomas of different histologic grade and receptor content.