ObjectiveTo understand which anthropometric diagnostic criteria best discriminate higher from lower risk of death in children and explore programme implications.DesignA multiple cohort individual data meta-analysis of mortality risk (within 6 months of measurement) by anthropometric case definitions. Sensitivity, specificity, informedness and inclusivity in predicting mortality, face validity and compatibility with current standards and practice were assessed and operational consequences were modelled.SettingCommunity-based cohort studies in twelve low-income countries between 1977 and 2013 in settings where treatment of wasting was not widespread.ParticipantsChildren aged 6 to 59 months.ResultsOf the twelve anthropometric case definitions examined, four (weight-for-age Z-score (WAZ) Z-score ConclusionsA combined case definition detects nearly all deaths associated with severe anthropometric deficits suggesting that therapeutic feeding programmes may achieve higher impact (prevent mortality and improve coverage) by using it. There remain operational questions to examine further before wide-scale adoption can be recommended.