Objective: To identify possible factors associated with undergoing bilateral salpingo-oophorectomy (BSO) at the time of hysterectomy among women with benign conditions. Methods: This was a cross-sectional analysis using the 2005 Nationwide Inpatient Sample. Women aged 18 years or older who underwent hysterectomy with BSO or hysterectomy only for a benign condition were included. We examined a broad range of factors associated with undergoing BSO in multivariable analyses. Results: Fifty-two percent of 461,321 hysterectomies included BSO, with a mean age of 49 years compared with 43 years in the hysterectomy-only group (P<.001). The odds of BSO were two times higher in the Midwest and South and 1.67 times higher in the West as compared with the Northeast (P<.001). Women who were uninsured or had Medicaid were more likely to undergo BSO compared with those with private insurance (odds ratio 1.86, 95% confidence interval 1.14-3.04 for "no charge/charity," odds ratio 1.21, 95% confidence interval 1.08-1.35 for Medicaid) Although BSO was more common among white women than African-American, Latina, and Asian women (P<.001), lower income was associated with BSO among African-American and white women only, not among Asian and Latina women (P=.007 for test for interaction). BSO was eight times as likely with a laparoscopic hysterectomy and 12 times as likely with an abdominal hysterectomy compared with a vaginal approach (P<.001). Women who had endometriosis, pelvic infection, or an ovarian cyst were more likely to undergo BSO (P<.001) compared with women who did not have these diagnoses. Conclusion: There is significant nationwide variation in the practice of BSO. Age, route of hysterectomy, and diagnosis at surgery affect BSO rates. Nonclinical factors such as race or ethnicity, insurance status, income, and geographic location are also associated with BSO practice. © 2009 by The American College of Obstetricians and Gynecologists. Published by Lippincott Williams & Wilkins.