We investigate the ability of quantitative measures derived from ultrafast DCE-MRI to improve breast MRI specificity for lesion diagnosis in a clinical setting. Sixty-nine women with BI-RADS 3, 4, or 5 lesions identified on clinical breast MRI exam, with subsequent diagnostic biopsy, were retrospectively identified. Ultrafast DCE-MRI was used to calculate semi-quantitative (bolus arrival time, max slope) and quantitative (Ktrans, vp) features for each lesion visible on the ultrafast series. Malignant lesions showed significantly higher vp compared to benign lesions. Combined with qualitative assessment of visibility on ultrafast DCE-MRI (“yes”/“no”), vp showed an AUC=0.73 for lesion diagnosis.