Three-dimensional data visualization is an important tool in several medical, scientific, and engineering areas. Visualization methods are based on a primitive representational element: contour, surface, or volume. Methods often incorporate options to cut open, see around, or see through structures, and form images in multiple windows or with animation. To visualize and interpret two or three related 3D data sets, composite imaging methods are required. The appropriate method depends on the user needs, application area, and available hardware. Visualization of 3D medical data is described for cranium/face, musculoskeletal systems, spine, intracranial structures, cardiovascular system, and radiation therapy.