Rapid volumetric helical CT has extended body CT imaging far beyond standard axial examinations. Technical improvements in high-resolution CT acquisition, coupled with advanced three-dimensional (3D) computer graphics, have permitted interactive 3D visualization in medical imaging. "Helical CT colonography" broadly refers to acquisition of planar helical CT images, with interactive display using a variety of two-dimensional (2D) and 3D visualization techniques to evaluate the colonic mucosa for colorectal polyps. "Virtual Colonoscopy" refers to computer-simulated 3D endoscopic visualizaton of the colonic mucosal surface. This rapidly growing field has gained multidisciplinary attention as a potential noninvasive test for colorectal polyps and cancer, with the hope that compliance will be increased, costs reduced, and diagnostic performance enhanced compared with current practice. Although marked technologic advances have been achieved, the challenges that lie ahead include standardization, validation, and implementation of these techniques in generalized settings. We review the current status of and future developments in image acquisition, image display, and clinical validation.