The goal of the Image Guidance Laboratories (IGL) is to provide the highest quality, real-time visualization of 3D ultrasound images in a manner that is most acceptable and suited for adoption by surgeons. To this end, IGL has developed an optically tracked, freehand, 3D volume- rendering ultrasound system for image-guided surgery. Other systems temporally separate frame acquisition from volume construction and display; the data must be stored before being loaded into the volume construction engine for visualization. By incorporating novel methods to reduce the computational expense associated with frame insertion, volume maintenance, and 2D texture-based rendering, the IGL system is able to simultaneously acquire and display 3D ultrasound data. The work presented here focuses on methods unique to achieving near real-time 3D visualization using 2D ultrasound images and discusses the potential of this system to address clinical situations such as liver resection, tumor ablation, and breast biopsy.