Abstract Background: Low carbohydrate diets and the DASH-style diet have not been evaluated for their association with breast cancer. Methods: We prospectively examined the association between the DASH score, overall, animal, and vegetable low carbohydrate diet scores and risk of postmenopausal breast cancer in 86,621 women in the Nurses’ Health Study. Diet scores were calculated from up to 7 food frequency questionnaires (FFQ) during up to 26 years of follow-up. We also examined the association with major plant food groups. Analysis was separately conducted for estrogen receptor status (ER) positive and negative tumors. Results: We ascertained 5,522 incident cases of breast cancer, including 3,314 ER+ and 826 ER- cancers. After adjusting for potential confounders, the DASH score was associated with a lower risk of ER- cancer (RR comparing extreme quintiles=0.80, 95% CI=0.64-1.01, p trend=0.02). However, this is largely explained by higher fruits and vegetables intake. An inverse association was also observed with the vegetable low carbohydrate score (corresponding RR=0.81, 95% CI=0.65-1.01, p trend=0.03). Total fruits and low protein vegetables were association with a lower risk of ER- cancer (RR comparing extreme quintiles=0.71, 95%CI=0.55-0.90, p trend=0.005). Conclusion: A diet high in fruits and vegetables, such as one represented by the DASH score was associated with a lower risk of ER- breast cancer. In addition, a diet high in plant protein and fat and moderate in carbohydrate content is also associated with a lower risk of ER- cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3740. doi:10.1158/1538-7445.AM2011-3740