This document discusses prioritizing agricultural research for development impact. It argues that decision analysis should be used to focus research on filling key knowledge gaps that affect important decisions, rather than trying to address all gaps. Decision analysis involves building a model of all factors influencing a decision, assessing current knowledge, and identifying which knowledge gains would be most valuable. As an example, the document describes using decision analysis to evaluate a controversial water pipeline project in Kenya. It concludes that development research could benefit from adopting decision analysis approaches to better support complex, risky decisions under uncertainty.