Because of rising health care costs, radiologists will increasingly be asked to provide scientific evidence to justify the use of diagnostic imaging. In the past, information about the diagnostic accuracy of imaging tests was sufficient; in the future, information about the impact of diagnostic imaging on patients' outcomes will be needed. In this article, some of the important aspects of technology assessment are discussed. All radiologists should become familiar with these concepts. The strengths as well as the limitations of different approaches must be appreciated in order for us to achieve our goal of providing the best care that we can for our patients.