There is a coming wave of novel genetic therapies aiming to treat rare pediatric disease. A large literature investigates the valuation of new treatments, but the valuation of treatments for rare pediatric illness raises a host of unique issues. In this paper, we review the challenges of applying both the standard economic model and standard approaches to estimating cost-effectiveness using the quality-adjusted life year (QALY) to this case. We argue that there are a large number of special issues that have only been partially addressed by past work and we conclude that more data and the development of new methods are vital as innovators, health technology assessment practitioners and policymakers confront the launch of these new drugs.https://www.nber.org/papers/w27978First author draf