Endometrial cancer is a hormone sensitive tumor. Response rate to progestational therapy is related to steroid receptor expression of the tumor. Interferons have been shown to enhance hormonal receptors. In this study the effect of four different interferons and medroxyprogesterone acetate (MPA), on three human endometrial cancer cell lines (AE-7, HEC-1A and HEC-1B), was studied. The ATP cell viability assay was used to measure the antiproliferative activity of the agents used. Synergistic effect was noted only when interferons and MPA were used in combination for the treatment of AE-7, which is the only cell line with a high baseline level of progesterone receptors. These observations indicate that the use of interferons and MPA may have a role for the treatment of endometrial cancer patients with progesterone receptor positive cells.