Surgical or percutaneous heart valve replacement has dramatically improved the outcomes of patients with significant heart valve disease in the past six decades. However, no ideal valve exists, and all prosthetic valves are prone to dysfunction. Echocardiography is the main noninvasive imaging modality for evaluating prosthetic valve structure and function. It should be noted that echocardiography of prosthetic heart valves is more demanding, to perform and interpret, than the assessment of native heart valves. Multiple parameters should be evaluated to determine the diagnosis and etiology of potentially life-threatening prosthetic valve dysfunction. This chapter will review the role of echocardiography in assessing the normal and abnormal function of the prosthetic heart valves, and the cause of prosthetic valve dysfunction, which is essential for proper treatment.