The joint effect of risk factors on endometrial cancer was examined by applying general statistical models to the data of a hospital-based case-control study conducted in Copenhagen, Denmark. The analysis included 149 cases of histologically confirmed adenocarcinoma of the endometrium and 154 age-matched controls with cervical cancer. Information on risk factors derived from the medical records. Estrogen use and body mass were found to be the main predictors of endometrial cancer risk. In the model proposed, women who ever used non-contraceptive estrogens had a 10-fold increased risk irrespective of their weight and height. Among non-users of estrogen, the risk of endometrial cancer rose with increasing body mass, the largest showing a five-fold increased risk. These data provide further evidence of the significant role that excess estrogens play, whether exogenous from replacement therapy or endogenous from enhanced androgen conversion, in the etiology of endometrial cancer.