This paper derives a dynamic cost-bene…t rule for evaluating large projects.We show that, in addition to the conventional income and consumer surplus measures, the rule also entails an extra term involving capital cost changes.JEL: D6, D9, H4.Keywords: cost-bene…t rule; large project; and capital cost.Chuan-Zhong Li, Department of Economics, Uppsala University, and Karl-Guataf Löfgren, Department of Economics, Umeå University. The authors would like to thank an anonymous referee for valuable comments and suggestions. The usual disclaimer applies.