The need for agricultural research resources in the developing world cannot be underestimated, but the availability of such resources is often poor due to lack of funding and investment. In order for Africa and other such developing countries to achieve productivity in agriculture - vital to food security, poverty reduction and sustainable management of natural resources - investment and policy development needs to be assessed. This book, a joint effort from IFPRI, ILRI and the Kellogg Foundation, explores the importance of impact assessment studies in Africa, and assembles important evidence to pave the way for further, much needed investment in agricultural research all over the developing world.