In this chapter, several important aspects related to dose and image quality in computed tomography (CT) have been discussed. The basic system design is discussed in the beginning. The dose and image quality concepts are presented afterward. The task-specific feature of the dose requirement is emphasized. More technical considerations are given in the dose reduction section. They include the discussions of the nonlinear response of image quality to dose, the effect of iterative reconstructions, low kV imaging for contrast studies, automatic tube current modulation, and the caveats of applying these techniques. Practical dose and protocol management aspects are addressed in the last section, such as standards and regulations, CT for pediatric and pregnant patients, and the suggestions for dose and protocol management.