From a sequence of computed tomograms of two-dimensional transverse slices of a body one can build up a three-dimensional array of numbers containing spatial rather than cross-sectional information. We have developed computer methods to display a slice at arbitrary orientation through the three-dimensional object. The three-dimensional array of numbers can also be used to display what any particular organ would look like if it were removed from the body. This is done by a computer technique that first detects the surface of the organ of interest and then displays this surface on a screen.