Iron deficiency is a widespread nutritional problem in developing countries, causing impaired physical activity and cognitive development, as well as maternal mortality. Although food fortification and supplementation programmes have been effective in some countries, their overall success remains limited. Biofortification, that is, breeding crops for higher micronutrient content, is a relatively new approach. We propose a methodology for ex-ante impact assessment of iron biofortification, which builds on disability-adjusted life years (DALYs) and a large household data set.