The paper deals with the problem of subject access and retrieval in large archival photography collections. One approach to concept control through a structured thesaurus for use in an automated catalogue database is identified. The Image Access Society, a group comprised of archivists, museum curators, librarians, and academics, has proposed that a major universal subject thesaurus such as the Library of Congress Subject Headings modified for prints and photographs by E. Betz could be a possible model upon which specialized thesaurus development could take place. This development process as applied to the National Photography Collection of the Public Archives of Canada is outlined. -- AATA