In a case-control study to evaluate risk factors for endometrial cancer, obesity, history of various diseases, reproductive and menstrual characteristics, marital status, education, and lifetime use of female hormones were examined in 173 histologically proven endometrial cancers and 347 controls. Obesity, non-contraceptive oestrogen use, late menopause, low parity and history of uterine fibromyomas were associated with an increased risk of endometrial cancer. The relative risks of obesity and oestrogen use seem to fit well for an additive model. Histological differentiation was positively correlated both to oestrogen use and to level of overweight, supporting the hypothesis of a specific role of oestrogens in endometrial cancer.