Prostate cancer is the most common cancer in the world, the most frequently diagnosed in the United States, and the second most lethal cancer in U.S. men. Earlier diagnosis implies better prognosis. However, prognosis may be dependent upon the stage of the malignancy at the time of diagnosis and implementation of appropriate therapy. Clinical staging, even with the development of serum prostate-specific antigen and other studies, has not proven to be highly accurate, particularly to identify and quantitate local disease and extension. Imaging has, in the past, also had limited success. With the development of computed tomography (CT), endorectal ultrasound, and magnetic resonance imaging (MRI). there was great expectations for improvement. However. CT and ultrasound have not been as accurate as hoped. MRI, because of its multiorientation and multiparameter abilities, has been the most definitive imaging tool for staging of local extension, yet still has limitations. The prostate capsule, the neurovascular bundles, the seminal vesicle, and other regions prone to initial attack by cancer extension can be seen exquisitely clearly by the newer approaches to MRI. Cancer extension, however, cannot be consistently identified when it is microscopic. MRI is an accurate identifier of macroscopic, even subtle macroscopic disease, but there are still limitations in its ability to diagnose all pathology.