25.1.        Introduction. The present chapter is based on IMTS 2010, chapter IX, on data quality and metadata. It describes all the information on the trade data that should be considered metadata. It explains that metadata are relevant for the correct understanding of the content, coverage and limitations of the data, and provides guidance on the correct interpretation of the trade statistics. Metadata exist at various levels of detail: at the overall level, metadata indicate the nature of the coverage of the trade statistics, and how data are collected and processed; at the next levels, information can be given on the main data variables, such as commodity classification, country nomenclature and country coverage, or valuation, and on specific trade flows. This chapter provides advice on and examples of how best to present and disseminate the metadata.