Recently Ultrasonography (US) and Magnetic Resonance Imaging (MRI) has been successfully used as painless and non invasive techniques for depicting dense fibrous connective tissue of Peyronie's Disease (PD). The purpose of this study is to demonstrate the extent of disease and to prove the accuracy of US versus MRI. Twenty patients (aged 20-70; mean 43) with clinical diagnosis of PD were studied. All patients were studied with flaccid and erected penis after an intracavernous injection of Papaverine (variable dose). US and MRI examinations were performed independently by 2 groups of observers who knew clinical findings but not the results of the other technique. Both methods gave satisfactory images: they show the capacity to depict and to measure Peyronie's plaques clinically appreciated. US in 4 patients and MRI in 3 patients identified not palpable lesion which infiltrate the septum. Although the most common area of PD involvement is the dorsal surface of tunica albuginea, sometimes fibrous plaques are along the septum between the corpora cavernosa and the corpus spongiosum. In the present study, US and MRI are too able to identify not palpable lesion in the septum. In our opinion US has to be used for its high accuracy and low cost.