We developed an interactive three-dimensional (3D) ultrasound (US) workstation that is inexpensive and suitable for use in research and clinical environments. Our personal computer-based system produces 3D volumes by acquiring a series of 2D images from a commercial ultrasound scanner, spatially registering the images using an electromagnetic position sensor, and reconstructing the data into a regular 3D Cartesian volume. The 3D US system uses an imaging board based on the Texas Instruments TMS320C80 Multimedia Video Processor (MVP), a fully programmable mediaprocessor that includes multiple processing units on a single chip. We developed efficient volume reconstruction and visualization algorithms for the MVP that allow our 3D US system to provide the same immediate feedback as current 2D US technologies with the added advantage of presenting information in three dimensions. For example, for acquired sequences of 512 ฯซ 512 US images, volumes can be reconstructed using six degree-of-freedom position measurements at 11.4 frames/s. A modified reconstruction algorithm that performs incremental reconstruction was developed to enable real-time volume reconstruction and visualization during acquisition and operates at 12.5 frames/s. US volumes can be rendered via shear-warp factorization and maximum intensity projection (MIP) at 10 frames/s for 128 ฯซ 128 ฯซ 128 volumes and 1.45 frames/s for 255 ฯซ 255 ฯซ 255 volumes.