Three-dimensional echocardiography (3DE) represents a major innovation and revolution in the field of cardiovascular ultrasound. Advances in computer and transducer technologies has permitted real-time 3DE acquisition and presentations 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 extensively reviewed. Introduction of xMATRIX technology has enabled utilization of more than 3000 fully sampled elements for 360o 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 speedy processing of the acquired data has resulted in creating images with high temporal and spatial resolutions in a single-beat acquisition format. Nowadays 3DE is becoming part of the routine echocardiography modality. 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 resolutions, motion and stitch artifacts, and lack of direct 3D measurements are the major limitations. Further technical improvements will heighten its role as the first cardiac imaging modality in our daily practice.