This report evaluates sources of international child well-being data to assess their suitability for supplementing national and transnational data sources to inform policy. The review of the leading surveys of children (and surveys of households with children) summarises the information available from these sources and, as importantly, identifies the gaps in measuring child well-being outcomes not covered by data from these sources. The report then undertakes an in-depth evaluation of possible systematic bias in the underlying survey population to provide confidence in the reliability of outcomes measured from these international surveys. Based on the overall evaluation, the report concludes with recommendations for the use and improvement of international surveys for monitoring child well-being.