After describing the technique, the authors recall the ultrasound anatomy of the prostate with the symmetrical echoes given by the seminal vesicles, the vas deferens and the ejaculatory ducts, which often allow a distinction to be made between the cranial and caudal portions of the prostate. Calculation of the volume (normally under 20 cm3) measures the enlargement (useful in determining the choice of approach), using the formula (Formula: see text) Ultrasound also often gives some idea of the nature of the lesion. The main distinction between an adenoma and a carcinoma is the fact that the adenoma is normally confined to the cranium. Carcinomas are generally asymmetrical, and their structure is non-echogenic, giving coarse echoes. Chronic prostatis, on the other hand, leads to the existence of symmetrical hyper-echogenic areas, sometimes calcified. The main contribution of suprapubic ultrasound is the information it provides concerning the repercussions on the urinary tract (residue, straining bladder, repercussions on the kidney). It can also be used to monitor developments.