The purpose of this study was to further investigate the role of estrogen but especially progesterone on epithelial ovarian tumor development since previous studies have suggested a relationship between serum progesterone, progesterone receptor expression and prognosis. Serum progesterone concentration, the immunohistochemical expression of estrogen receptor alpha (ER), progesterone receptor A/B (PR), Ki-67, Bcl-2, p53, apoptosis and morphology were determined in 33 patients, all with poorly differentiated surface epithelial ovarian tumors of different types. ER was expressed in 79% and PR in 33% of the tumors. This group of aggressive tumors was highly proliferative as indicated by Ki-67 index (mean 38.9%), and in some cases proliferation appeared to be mainly located to areas with a high ER density. The majority of cases (76%), both receptor-positive and -negative, overexpressed p53. High ER expression was related to a lower apoptotic activity as compared with tumors with a low expression of the ER (p = 0.008). Serum progesterone in itself did not show any clear relationship to steroid receptor status, expression of Ki-67, p53, Bcl-2 or signs of apoptosis. Survival in this small but homogeneous group of advanced epithelial ovarian cancers, showed an improved survival rate in patients with high serum progesterone, especially in combination with expression of progesterone receptors (p = 0.04). In conclusion, estrogen and progesterone receptors in parallel with deranged p53 and Ki-67 were expressed to a great extent. The finding of a lower apoptotic activity in tumors with a high expression of ER and an indication of increased proliferation in areas with high ER density gives a rationale for antiestrogen therapy even in poorly differentiated epithelial ovarian cancers. Improved survival is related to serum progesterone, especially in combination with PR expression.