Prostate cancer is the most prevalent malignancy in the world. It is the most frequently diagnosed cancer in the American male population and the second most lethal cancer in American men. However, concurrent benign prostatic hyperplasia occurs in almost all men developing the malignancy (although the two processes are unrelated) and many others who have no evidence of cancer. Imaging evaluation of the prostate can be for diagnostic or staging purposes. While MRI can be used on occasion for diagnostic evaluation of prostatic disease, it is most often reserved for evaluation of men with known pathology. The use of MRI is important to plan the appropriate therapeutic approach to men with prostate cancer. An understanding of the newer concepts of anatomy, origins of disease, spread of cancer, and the clinical implications of pathological change of the prostate are important and are discussed in this article. The uses of MRI, the deficiencies of the study, the techniques needed to utilize the modality appropriately, and diagnostic criteria and limitations are also discussed.