OBJECTIVE To survey the results of mass screening for cancer of the endometrium performed over a six-year period in Miyagi Prefecture, Japan. METHODS Materials were cytodiagnostic samples of the endometrium examined by the Miyagi Cancer Society. The samples were classified into two groups: The mass screening group, from whom samples were collected according to the Health and Medical Service Law for the Aged, and the outpatient group, consisting of samples from other patients. The rates of subjects judged to require close examination and the detection rate of cancer of the endometrium in the two groups were compared. RESULTS In the mass screening group, the rate of subjects judged to require close examination and the detection rate of cancer of the endometrium were 2.3% and 0.11%, respectively, while they were 5.9% and 0.39%, respectively, in the outpatient group; the differences between the two groups were significant. CONCLUSIONS To improve the detection rate in mass screening for endometrial cancer according to the Health and Medical Service Law for the Aged, it is necessary to establish a new criterion for selecting subjects.