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BACKGROUND More evidence is needed to substantiate current recommendations about removing ovaries during hysterectomy for benign conditions. OBJECTIVE To compare long-term outcomes in women with and without bilateral salpingo-oophorectomy (BSO) during hysterectomy for benign conditions. DESIGN Emulated target trial using data from a population-based cohort. SETTING Women in Denmark aged 20 years or older during 1977 to 2017. PARTICIPANTS 142 985 women with hysterectomy for a benign condition, 22 974 with BSO and 120 011 without. INTERVENTION Benign hysterectomy with or without BSO. MEASUREMENTS The primary outcomes were overall hospitalization for cardiovascular disease (CVD), overall cancer incidence, and all-cause mortality through December 2018. RESULTS Compared with women without BSO, women with BSO who were younger than 45 years at surgery had a higher 10-year cumulative risk for hospitalization for CVD (risk difference [RD], 1.19 percentage points [95% CI, 0.09 to 2.43 percentage points]). Women with BSO had a higher 10-year cumulative risk for cancer for ages 45 to 54 years (RD, 0.73 percentage point [CI, 0.05 to 1.38 percentage points]), 55 to 64 years (RD, 1.92 percentage points [CI, 0.69 to 3.25 percentage points]), and 65 years or older (RD, 2.54 percentage points [CI, 0.91 to 4.25 percentage points]). Women with BSO had higher 10-year mortality in all age groups, although the differences were statistically significant only for ages 45 to 54 years (RD, 0.79 percentage point [CI, 0.27 to 1.30 percentage points]). The mortality at 20 years was inconsistent with that at 10 years in women aged 65 years or older. LIMITATION Age was a proxy for menopausal status. CONCLUSION The authors find that these results support current recommendations for conserving ovaries in premenopausal women without a high risk for ovarian cancer and suggest a cautious approach in postmenopausal women. PRIMARY FUNDING SOURCE The Danish Cancer Society's Scientific Committee and the Mermaid Project.