DESCRIPTION: (Adapted from the Application): The investigators propose to develop and validate a three-dimensional computed tomography technique for evaluating the human colon for the presence/absence of polyps that will be as sensitive as colonoscopy (95%) and have a specificity greater than or equal to 80%. Virtual endoscopic views will be produced that may eliminate a large fraction of colonoscopy exams which would have negative results and also would have involved higher risk, discomfort and cost. The three specific aims toward this objective include: (1) development of an optimized spiral CT scanning protocol, (2) visualization technique development and evaluation for three different types of reconstruction software, and (3) clinical validation in a 170 patient study over the four year project duration.