Magnetic Resonance Imaging of 20 patients with local prostatic carcinoma was correlated with pathological findings after radical prostatectomy. The tumor was always seen with an hyposignal, associated in 6 cases with benign prostatic hyperplasia. Extracapsular extension was correctly evaluated (17 cases/20). There were 6 false positive diagnosis of seminal vesicles extension among 40 cases because of an hyposignal in intact vesicles and one false negative diagnosis. Magnetic Resonance Imaging is a good exam to appreciate loco-regional extension of prostatic carcinoma.