Modeling fiber architecture within the white matter. Thus, presurgical brain mapping presents the challenge of integrating and visualizing multiple representations of brain anatomy, including functional cortical areas, functional white matter tracts, and their underlying structural anatomic substrate. We have previously presented work describing a tool for integrated volume visualization of fMRI and conventional structural MRI [1]. The object of the present work is to extend this tool to further incorporate white matter fiber track geometry. Visualization issues that we consider include the mixing of voxel-based and geometry data, volume rendering techniques, graphics hardware techniques, and user interface design.