A Briefing Note for policy makers and programme implementers. This policy brief is an is the culmination of the research and discussion of the ENN-coordinated Wasting-Stunting (WaSt) Technical Interest Group (TIG) over the last 4 years and presents the compelling scientific grounds for concluding that the current separation between wasting and stunting in policy, programmes and research is not justified and may even be detrimental. Greater programming efficiency and effectiveness can be realised if both forms of undernutrition are jointly tackled. This will require a radical change in how we view, finance and intervene to reduce child wasting and stunting.