This sourcebook draws on the emerging principles of Agricultural Innovation System (AIS) analysis and action to help to identify, design, and implement the investments, approaches, and complementary interventions that appear most likely to strengthen innovation systems and promote agricultural innovation and equitable growth. Although the sourcebook discusses why investments in AISs are becoming so important, it gives most of its attention to how specific approaches and practices can foster innovation in a range of contexts. The sourcebook is targeted to the key operational staff in international and regional development agencies and national governments who design and implement lending projects and to the practitioners who design thematic programs and technical assistance packages. The sourcebook is also an important resource for the research community and nongovernmental organizations (NGOs) and may be a useful reference for the private sector, farmer organizations, and individuals with an interest in agricultural innovation. It concludes with details on the sourcebook's structure, a summary of the themes covered in each module, and a discussion of the cross-cutting themes treated throughout the sourcebook.