There has been a tremendous advance in echocardiography over the past decades. Recently, the advent of real-time three-dimensional echocardiography (3-D echo) has opened a new era in medical ultrasound. It greatly reduces the image acquisition and reconstruction times and simplifies the examination. It has several advantages over two-dimensional echocardiography. First, it can show the cardiac structures from any viewing angle. For example, it can provide a "surgeon's view", mimicking operative findings. This feature also contributes significantly to the clarification of the complex anatomy in congenital heart diseases, and to the understanding of the mechanism of invasive interventions. Second, it can measure cardiac volumes accurately and reproducibly, without the need of geometric assumptions. Third, some important information (such as strain and strain rate) can be derived in a three-dimensional format, which is very useful for cardiac resynchronization therapy. However, 3-D echo is still immature. Further improvements in its image resolution and analysis capability are required before it can become a truly versatile and indispensible imaging modality.