We argue in this paper that a shared desire to find a solution to malnutrition and agreement at a broad level concerning priority, evidence-based interventions are important but not sufficient conditions for effective policy development. This paper illustrates this point, and draws out general implications, through a detailed analysis of a case in which conflict emerged when committed nutrition policy actors began discussing the details of program design and implementation. The case involves one country's effort to select "the best" anthropometric indicator for use in its national child growth-monitoring program. In this case the interested parties approached this deceptively simple decision for different reasons, using different sources and standards of evidence and focusing their attention on opposite, but equally critical, operational considerations, while being heavily influenced by global, national, and interorganizational events and relationships. We suggest that actors seeking to translate political commitment for nutrition into effective action should recognize the technical and sociopolitical complexity of seemingly simple decisions related to intervention design and employ more systematic, intentional, and inclusive decision-making procedures. Without attention to such practical matters, the current window of opportunity to reduce malnutrition on a global scale may quickly close.