Ignoring costs when evaluating different measures is not a very rational way to deal with fire safety. Finding efficient measures to increase fire safety is a necessary, but not sufficient condition for choosing the relevant measure. The measure in question must also be economically efficient, that is, the benefits must outweigh the costs, both measured in monetary values. Cost-benefit analysis, CBA, is a method used to find out if that is true or not. This chapter describes what CBA is and how to use it for evaluating fire safety measures. The problem of choosing values for lives and injuries is discussed. The chapter also includes a short list of CBA results for residential fire safety measures. The main conclusion of the chapter is that more CBA studies evaluating fire safety measures should be done.