A review of literature, mainly the results of studies conducted in America, shows obesity, diabetes mellitus, hypertension, infertility/nulliparity, late menopause, high endogenous oestrogen production, and the use of oestrogens to be the main factors associated with the development of endometrial carcinoma. Whilst most of these factors undoubtedly apply irrespective of country, doubt in Finland about the use of oestrogens being a risk factor was one of the reasons prompting the study reported here. This study, which was conducted in Turku, Finland, involved 318 endometrial carcinoma patients, 282 of whom could be paired with controls matched for age, height and weight, and social class. The data show the use of oestrogens per se not to be a risk factor. The fact that there appears to be a risk in America, where most of the oestrogenic preparations used are based on conjugated equine oestrogens, but not in Finland, where the preference is for preparations based on oestriol and oestradiol and where conjugated oestrogen preparations are relatively rarely used, supports the hypothesis that the risk depends on the type of oestrogen used.