Objective: We sought to determine whether prophylactic oophorectomy rates changed after the introduction of a 2007 health plan clinical guideline recommending systematic referral to a genetic counselor for women with a personal or family history suggestive of an inherited susceptibility to breast/ovarian cancer.Methods: We conducted a retrospective cohort study of female members of Group Health, an integrated delivery system in Washington State. Subjects were women aged ≥ 35 years during 2004-2009 who reported a personal or family history consistent with an inherited susceptibility to breast/ovarian cancer. Personal and family history information was collected on a questionnaire completed when the women had a mammogram. We ascertained oophorectomies from automated claims data and determined whether surgeries were prophylactic by medical chart review. Rates were age-adjusted and age-adjusted incidence rate ratios (IRR) and 95% confidence intervals (CI) were computed using Poisson regression.Results: Prophylactic oophorectomy rates were relatively unchanged after compared to before the guideline change, 1.0 versus 0.8/1000 person-years, (IRR=1.2; 95% CI: 0.7-2.0), whereas bilateral oophorectomy rates for other indications decreased. Genetic counseling receipt rates doubled after the guideline change (95% CI: 1.7-2.4) from 5.1 to 10.2/1000 person-years. During the study, bilateral oophorectomy rates were appreciably greater in women who saw a genetic counselor compared to those who did not regardless of whether they received genetic testing as part of their counseling.Conclusion: A doubling in genetic counseling receipt rates lends support to the idea that the guideline issuance contributed to sustained rates of prophylactic oophorectomies in more recent years.