This was a two-phase, large sample-group study assessing the effectiveness of combined transvaginal sonography (TVS) and endometrial cytology in endometrial cancer screening. In phase one, 3308 women without known cancer were enrolled and TVS was performed on those with symptoms or endometrial cancer risk factors. Endometrial cytology was carried out on post-menopausal women with endometrial thickness >or= 5 mm and on pre-menopausal women with endometrial thickness >or= 10 mm. Dilation and curettage (D & C) was performed if cytological findings were inconclusive, or indicated cancer or pre-cancer. The mass screening safety interval is at least 2 years and phase two was carried out 2 years after phase one, using the same procedures, on the 3305 women who were originally found to be cancer free. Combined TVS and endometrial cytology resulted in 100% sensitivity and 99.0% specificity, reducing unnecessary D & C by 91.7% and screening costs by 20.1%. Combined TVS examination and endometrial cytology decreased potentially harmful examinations, patient suffering and medical costs, and is worth considering for broad implementation.