To investigate the ability of high field ex vivo magnetic resonance imaging (MRI) to localize prostate cancer (PCa) and to predict the margin status in fresh radical prostatectomy (RP) specimens using histology as the reference standard. This Institutional Review Board (IRB)-approved study had written informed consent. Patients with biopsy-proved PCa and a diagnostic multiparametric 3T MRI examination of the prostate prior to undergoing RP were prospectively included. A custom-made container provided reference between the 7T ex vivo MRI obtained from fresh RP specimens and histological slicing. On ex vivo MRI, PCa was localized and the presence of positive surgical margins was determined in a double-reading session. These findings were compared with histological findings obtained from completely cut, whole-mount embedded, prostate specimens. In 12 RP specimens, histopathology revealed 36 PCa lesions, of which 17 (47%) and 20 (56%) were correlated with the ex vivo MRI in the first and second reading session, respectively. Nine of 12 (75%) index lesions were localized in the first session, in the second 10 of 12 (83%). Seven and 8 lesions of 11 lesions with Gleason score >6 and >0.5 cc were localized in the first and second session, respectively. In the first session none of the four histologically positive surgical margins (sensitivity 0%) and 9 of 13 negative margins (specificity 69%) were detected. In second session the sensitivity and specificity were 25% and 88%, respectively. Ex vivo MRI enabled accurate localization of PCa in fresh RP specimens, and the technique provided information on the margin status with high specificity. 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:439-448.