Clinical investigation is still fundamental in the diagnosis of La Peyronie's disease. In this study 36 patients underwent clinical investigation and ultrasound in basal conditions and during drug-induced erection, and the results were compared. In basal condition US does not provide much useful supplementary informations. During drug-induced erection US accurately visualizes plaque site and dimensions and anatomical abnormalities about corpora cavernosa, albuginea, septum and dorsal vessels.