Since 1990s to date, there has been a growing global interest among researchers in impact assessment of research and development (R&D). Attention has specifically been placed on the impact of R&D interventions on target beneficiaries. In this regard, this work, besides reviewing studies on impact assessment of agricultural research in Tanzania it documents the experience of Tanzanian farmers in the use of innovations by focusing on rice research-based innovations. Adaptation rather than adoption of innovations is evident in smallholder rice farming. Moreover, it sheds light on the limitation of the production-based reductionist approach in assessing the impact of research on food security. The economic costs and benefits of rice research in rain-fed agriculture in Tanzania are also presented. In general, this book should be of great interest to students in agricultural extension, rural sociology, agricultural economics, development studies as well as managers of agricultural research.