A rich set of metadata is required to integrate data values into a materials data-base. These metadata range from descriptions of the materials involved, the properties, independent variables, units, source of the data value, associated statistical descriptors, footnotes, and references. They are necessary to ensure the integrity of the database, to provide compatibility of data values arising from different sources, and to accommodate the diverse backgrounds of users with respect to terminology usage. The metadata issues covered include: materials characterization, terminology and standardization, implicit metadata in printed exhibits of data values, problems of developing a metadata thesaurus, testing for completeness of canonical or basic data records, use of metadata in data entry, and the identification of hypertext links for materials databases. Resolution through coordinated standardization of terminology and consistency of metadata will ensure further development of compatible materials databases.