Three-dimensional echocardiography (3DE) represents a major innovation and revolution in the field of cardiovascular ultrasound. Advances in computer and transducer technologies have permitted real-time 3DE acquisition and presentation of cardiac structures from any spatial point of view. 3D transesophageal echocardiography (3D TEE) creates a “common language” between echo cardiologist, cardiac surgeon, and cardiac interventionist in the operating room and cath lab for appropriate decision-making. In this chapter, technical background and modes of image acquisition are reviewed. Introduction of xMATRIX technology has enabled utilization of more than 3000 fully sampled elements for 360° focusing and steering. With this powerful technology built in echo probes, any plane of the heart can be imaged. Further advancements in computer technology in rapid processing of the acquired data has resulted in creation of images with high temporal and spatial resolution in a single-beat acquisition format. Nowadays, 3DE is part of the routine echocardiogram. Its role in diagnosis and management of valvular heart disease, cardiac chamber quantification, cardiac masses, and congenital heart disease are discussed in this chapter. The emerging and unique role of 3D TEE in guiding surgical and percutaneous interventions are of importance and will be discussed as well. 3DE is a new modality and like any other new techniques has its own limitations and pitfalls. Low spatial and temporal resolution, motion and stitch artifacts, and lack of direct 3D measurements are some limitations. Further technical improvements will heighten its role as the first cardiac imaging modality in our daily practice.