PIP: The authors have become convinced that estrogen therapy for postmenopausal disturbances is often beneficial but they are perturbed by reports of such therapy causing endometrial cancer. The use of progestational compounds with the estrogen medication in hormone replacement regimens is noted as approved by others. Nevertheless, cases of endometrial cancer following use of an estrogen-progestogen oral contraceptive have been reported. It is suggested that such patients may have "islands" of endometrium refractory to the progestogen component and reactive only to estrogen. In such foci, endometrial cancer may develop.