Since indexing systems concentrate upon the information content of materials and not upon their form, instructional media centers (IMC) can use one system for all media. Content descriptors can be selected from a thesaurus of accepted terms, from the title of the material, or from an analysis of the content. The first of these three methods is the most satisfactory for dealing with multiple forms of media; the Sears List of Subject Headings and Subject Headings used in the Dictionary Catalogs of the Library of Congress are the most commonly used thesauri. It is recommended that the main file index of the IMC contain all entries for all materials and that in-depth indexing be provided through use of several descriptors for each item. Lastly, catalog card files should be employed wherever possible. (PB)