This paper begins with a brief description of the importance of cassava in Mozambique, the incidence and consequences of brown streak, and the scope of the NGO Save the Children/U.S. program to propagate brown streak tolerant cassava planting material that is largely responsible for the dissemination of Nikwaha. Benefits are discussed extensively; a reasonable and conservative estimate of the per plant benefits of Nikwaha is the key parameter in the analysis. The early acceptance of Nikwaha is reviewed, and its diffusion over time is projected. The intervention is cast as a project and is appraised in the setting of a cost-benefit analysis. In the conclusions, we examine the limitations of our calculation on economic impact, identify areas for research, evaluate the prospects for more investment in extension, and draw lessons from Save the Children’s Nikwaha experience.