Multislice or multidetector CT is a relatively new technology that offers great potential as a screening tool because it is fast, potentially very accurate, and relatively noninvasive. During the last few years, many institutions in the United States have established screening programs for pulmonary cancer and colorectal adenomatous polyps using single and multislice helical CT. Establishing an effective screening program, however, is not a trivial task. We cannot assume that early detection of disease translates into improved patient outcome. In fact, early detection of disease can lead to higher morbidity and mortality rates. The issues involved in effective screening are complex and multifaceted.