A population-based case-control study of 109 women with invasive squamous-cell cervical cancer and 545 controls matched for age and area of residence was carried out in Jingan, China, to evaluate the importance of different risk factors and the effect of cervical cancer screening. After controlling for the protective effect of cervical cancer screening, several factors were found to make an independent contribution to risk. These included the number of sexual partners of the subjects and their husbands (OR: 3.9 for 2 or more sexual partners other than the current spouse, relative to none; 5.9 for 2 or more other partners of the husband relative to none), and poor genital hygiene (OR: 4.8 for absence of daily genital washing relative to washing every day; 0.3 for use of sanitary napkin), these are consistent with an infectious etiology. In addition, menstrual characteristics also had a strong relationship to the risk of cervical cancer (OR: 2.2 for 4 or more days' menstruation relative to shorter duration; 5.4 for irregular menstruation).