Obesity is associated with higher cervical cancer mortality, but its relationship with sexual behavioral risk factors that predispose women to human papilloma virus (HPV) and cervical cancer is unclear. We used data from 3,329 women participants, aged 20-59 years, of the 1999-2004 National Health and Nutrition Examination Survey, to analyze the relationship between BMI and age at first intercourse, number of sexual partners, condom use during sexual activity, history of sexually transmitted disease (STD), herpes simplex virus 2 (HSV-2) seropositivity, and HPV prevalence. BMI was not associated with the prevalence of HPV. Mildly obese women (BMI 30.0-34.9 kg/m(2)) were least likely to report a STD history (9% vs. 13% in normal weight) and >or=2 sexual partners in the previous year (8% vs. 13%) while overweight women (BMI 25.0-29.9 kg/m(2)) were least likely to report >or=10 lifetime partners; among those with multiple partners, BMI was not associated with sexual activity without condoms in the past month. After adjustment for age, race/ethnicity, and education, women with higher BMI were less likely to report sexual behavioral risk factors than normal-weight women; however, odds ratios were only significant for mildly obese women for reporting a STD history (0.74, 95% confidence interval 0.55-0.99) and having >or=2 sexual partners in the last year (0.57, 0.39-0.85). Higher BMI was not associated with HSV-2 seropositivity after adjustment. HPV and sexual behavioral risk factors for HPV and cervical cancer are not more prevalent in obese than normal-weight women and unlikely to account for higher-observed cervical cancer mortality in obese women.