Patients with fertility problems may be referred for scrotal ultrasonography (US) to evaluate testicular size, to assess testicular parenchyma, to examine epididymal integrity, and to ascertain the presence of varicocele. The scrotal ultrasound scan is carried out with the patient in the supine position, exposing the scrotum with the thighs and the abdomen covered. The testis, epididymal head, epididymal body, and epididymal tail are examined sequentially. Pulsed Doppler is also utilized to detect a subclinical varicocele by demonstrating the presence as well as the duration of reverse venous flow in the testicular veins. The use of ultrasound-guided testicular sperm aspiration in azoospermic patients has been described. A 21-gauge butterfly needle is directed into the testicular regions to be sampled under real-time gray-scale and power Doppler sonographic guidance, avoiding the echogenic mediastinum testis and the vascular plexus of the tunica albuginea, as well as the prominent testicular parenchymal vessels.