2 24–49 50–56 57–66 ≥67 White Black Other No Yes 0 <1–4 5–9 ≥10 No Yes No Yes Variable Age group, years Ethnic group Education Less than high school High school Posthigh school Family history of ovarian cancer No Yes Live births None Any Tubal ligation Oral Contraception, years Menopausal status Premenopausal Postmenopausal Self-report PID Self-report gonococcal or chlamydial cervicitis Infectious Diseases in Obstetrics and Gynecology Table 1: Frequencies of demographic and reproductive characteristics by case/control status. Case subjects no. (%) Control subjects no. (%) 135 (25.9) 111 (21.3) 129 (24.8) 146 (28.0) 495 (95.0) 19 (3.6) 7 (1.3) 46 (8.8) 180 (34.5) 295 (56.6) 487 (95.3) 24 (4.7) 124 (23.8) 397 (76.2) 389 (78.3) 108 (21.7) 223 (42.8) 205 (39.3) 59 (11.3) 34 (6.5) 142 (30.4) 325 (69.6) 515 (98.8) 6 (1.2) 502 (96.4) 19 (3.6) 204 (26.6) 208 (27.2) 187 (24.4) 167 (21.8) 736 (96.1) 20 (2.6) 10 (1.3) 37 (4.8) 229 (29.9) 500 (65.3) 731 (97.3) 20 (2.7) 104 (13.6) 662 (86.4) 490 (65.0) 264 (35.0) 214 (27.9) 321 (41.9) 134 (17.5) 97 (12.7) 194 (29.9) 454 (70.1) 759 (99.1) 7 (0.9) 736 (96.1) 30 (3.9) χ2 (P value) 9.29 (.026) 1.14 (.57) 13.56 (.001) 3.74 (.053) 22.23 (.000) 25.3 (.000) 40.02 (.000) .028 (.87) .18 (.68) .062 (.80) their gynecologists. Eligible women were at least 25 years of age and within 9 months of initial diagnosis. Controls consisted of women at least age 25 who lived in telephone exchanges wherein cases resided. Random digit dialing was used to identify age-eligible women, and these were further screened by the study team to ensure that they had not had a previous oophorectomy or diagnosis of ovarian cancer. Eligible women were then invited to participate. Potential controls were frequency matched by 5-year age group and telephone exchange to cases in an approximately 2:1 ratio. Women were interviewed in their homes by trained interviewers. The questionnaire included a reproductive and gynecological history, a contraceptive history, a medical his- tory, a family history, and information on lifestyle practices. We were able to draw blood on 92.5% of the interviewed cases and 84.4% of the interviewed controls. Blood samples were processed within 2 hours of collection by a laboratory technician. For this analysis, we selected the ﬁrst 521 cases and 766 controls with complete questionnaires, tumor registry (e.g., histology) information, and adequate serum samples.