It has been estimated that approximately 2% of the general population has a family history that is indicative of hereditary breast/ovarian cancer. We aim to further document the proportions of women identified by several protocols as having a positive family history of breast/ovarian cancer, as a prelude to offering genetic counseling and BRCA1/2 mutation testing. This is a critical component of the evidence base needed when considering implementation of family history screening in primary care. We apply six separate family history screening protocols for breast/ovarian cancer to four cohorts of women, 21 to 55 years of age, for whom self-reported personal, and first and second degree family histories of breast/ovarian cancer have been obtained. We analyzed family history for 3,073 women in the four cohorts. The screen positive rates among the protocols vary widely both within and among the cohorts. In Cohort 4, the screen positive rate ranges between 6.9% to 20.8%, depending on the protocol. Applying one of the protocols to the four cohorts yields screen positive rates between 5.0% and 16.7%. The proportion of women that is screen positive on all six protocols (or three, if Ashkenazi Jewish) ranges from 1.9% to 4.0%. Used alone, none of the recommended family history protocols yields an acceptable screen positive rate. A more acceptable 2% to 4% screen positive rate can be expected when all six protocols agree.