To compare the long-term risks associated with salpingo-oophorectomy with ovarian conservation at the time of benign hysterectomy. MEDLINE, ClinicalTrials.gov, and the Cochrane Central Register of Controlled Trials were searched from inception to January 30, 2015. We included prospective and retrospective comparative studies of women with benign hysterectomy who had either bilateral salpingo-oophorectomy (BSO) or conservation of one or both ovaries. Reviewers double-screened 5,568 citations and extracted eligible studies into customized forms. Twenty-six comparative studies met inclusion criteria. Studies were assessed for results, quality, and strength of evidence. Studies were extracted for participant, intervention, comparator, and outcomes data. When compared with hysterectomy with BSO, prevalence of reoperation and ovarian cancer was higher in women with ovarian conservation (ovarian cancer risk of 0.14-0.7% compared with 0.02-0.04% among those with BSO). Hysterectomy with BSO was associated with a lower incidence of breast and total cancer, but no difference in the incidence of cancer mortality was found when compared with ovarian conservation. All-cause mortality was higher in women younger than age 45 years at the time of BSO who were not treated with estrogen replacement therapy (hazard ratio [HR] 1.41, 95% confidence interval [CI] 1.04-1.92). Coronary heart disease (HR 1.26, 95% CI 1.04-1.54) and cardiovascular death were higher among women with BSO (HR 1.84, 95% CI 1.27-2.68), especially women younger than 45 years who were not treated with estrogen. Finally, there was an increase in the prevalence of dementia and Parkinson disease among women with BSO compared with conservation, especially in women younger than age 50 years. Clinical practice guidelines were devised based on these results. Bilateral salpingo-oophorectomy offers the advantage of effectively eliminating the risk of ovarian cancer and reoperation but can be detrimental to other aspects of health, especially among women younger than age 45 years.