The effects of the endocrine milieu on growth, invasion and metastasis, associated with neovascularization of endometrial cancer, the expression of plasminogen activator inhibitor 1 (PAI-1), and its mRNA in endometrial atypical hyperplasia and cancer, and normal endometria as controls were determined in premenopausal and postmenopausal women. In pre-menopausal women, the levels of PAI-1 and its mRNA in normal endometria were significantly higher than in endometrial atypical hyperplasia and cancer. On the other hand, in postmenopausal women, the results were reversed. There was no difference in the expression of PAI-1 and its mRNA in the various histological grades and clinical stages in endometrial cancers, while the expression of PAI-1 in other cancers increased during tumor progression. In our previous study, the expression of PAI-1 and its mRNA in well-differentiated endometrial cancer cell lines was dependent upon estrogen and progesterone. This might be partially related to the endocrine milieu, especially in endometrial atypical hyperplasia and well-differentiated endometrial cancer, which seems to be dependent on sex steroids. Therefore, endometrial cancer of any histological grade and clinical stage might maintain PAI-1 expression in both premenopausal and postmenopausal women, which may modulate, at least in part, growth, invasion and metastasis associated with neovascularization of endometrial cancer.