Estrogen and progesterone receptor concentrations were measured in the primary tumors of 137 surgically staged women with clinical stages I and II endometrial carcinoma. For each steroid, increasing receptor concentrations were associated with a decrease in hazard (increase in survival) and the effect was linear for each receptor. When expressed dichotomously, steroid receptor status was also significantly associated with a number of known risk factors, and the significance of the association was influenced by the receptor concentration used as the criterion for receptor positivity. In a multivariate analysis, only progesterone receptor concentration affected survival independently, but the effect disappeared when the analysis was restricted to women with disease confined to the uterus. We conclude that the estrogen and progesterone receptor status of the primary tumor is of limited prognostic significance in endometrial carcinoma unless extrauterine disease is present.