Penile ultrasound is commonly used in the diagnostic workup of patients with erectile dysfunction (ED), but also plays an important role by providing an anatomic and functional assessment in a multitude of other conditions including Peyronie’s disease, priapism, penile fracture, penile urethral strictures, urethral stones, or diverticulae, or masses involving deep tissues of the penis. As a component of the evaluation for ED, penile Doppler ultrasound (PDU) is performed to assess the quality of arterial blood flow and sufficiency of veno-occlusive mechanisms, both necessary for adequate erections. More recently, PDU is playing a central role in the early detection of otherwise silent coronary artery disease (CAD) in men presented with ED as their initial symptom. PDU is also an essential component of the assessment of external genitalia in trauma situations. Penile ultrasound provides a readily available, minimally invasive diagnostic modality that evaluates both the structural anatomy and functional hemodynamics.