Purpose: To assess the quantity and frequency of hemorrhage after prostatic biopsy. As post-biopsy blood products may interfere with interpretation of MR images, we also investigated the optimal timing for MR examination after biopsy. Material and Methods: Fifteen patients scheduled for prostatic biopsies were imaged with endorectal MR before and after the procedure. In addition, MR studies of 42 patients with prostate cancer were retrospectively analyzed. The amount of post-biopsy blood product and the degree of its interference with image interpretation were assessed. Results: Of a total of 57 patients, 44 (77%) had visible post-biopsy hemorrhage. However, the presence of blood products were considered to interfere with interpretation of the images in only 12 (21%) cases. This disturbing effect seems to diminish after 21 days from biopsy. The total amount of blood clearly decreased after 28 days. Conclusion: Deferring MR imaging for at least 3 weeks after prostatic biopsy is advisable. T1-weighted images are necessary to rule out false-positive findings caused by post-biopsy hemorrhage.