The results of a cervical cancer screening program in a population of 22,106 women aged over 25 years in a rural county of China are evaluated in a case-control analysis. The relative risk of cervix cancer was 0.33 in women with three or more negative tests (compared with one or less) and 11.4 for women whose last negative smear was 8 or more years previously (compared with 2 years or less). Attendance at the screening program was positively associated with some risk factors for cervix cancer (sexual behavior of the woman and her partner) and negatively associated with others (genital hygiene). Controlling for the confounding effect of these risk factors resulted in only small changes in the estimate of the protective effect of screening.