Abstract: The role of magnetic resonance imaging (MRI) in patients with newly diagnosed breast cancer is somewhat controversial. The purpose of this study was to evaluate the prevalence of synchronous, occult contralateral breast cancer detected by MRI but not by mammography or clinical breast examination in women with newly diagnosed breast cancer, including those aged 70 years or older at our institution. MRI results for women with newly diagnosed breast cancer who underwent bilateral breast MRI after negative mammography and clinical examination between February 2003 and November 2007 at Mayo Clinic in Florida were reviewed. The prevalence of pathologically confirmed contralateral carcinoma diagnosed solely by MRI was determined and analyzed in the context of age, family history, menopausal status, breast density, and primary-tumor characteristics. Logistic regression was used to explore the association between contralateral carcinoma and potential patient risk factors. A total of 425 women were evaluated, of whom 129 (30%) were aged 70 years or older. A contralateral biopsy was recommended and performed solely on the basis of MRI in 72 of the 425 women (17%). Sixteen of these 72 women (22%) had pathologically confirmed carcinoma, including seven in the older subgroup. The prevalence of clinically and mammographically occult contralateral carcinoma detected by MRI was 3.8% (16/425) overall and 5.4% (7/129) in the group of older women. When potential risk factors for contralateral breast cancer were evaluated, postmenopausal status was the only significant predictor of contralateral cancer detected by MRI (p = 0.016). We concluded that contralateral breast screening with MRI should be considered in postmenopausal women with newly diagnosed breast cancer, even those aged 70 years or older at diagnosis.