Precoordination of Library of Congress Subject Headings (LCSH), in both the LCSH thesaurus and online public access catalog (OPAC) browse displays, continues to be necessary for several reasons: (1) the meaning of thousands of LCSH headings depends on their word order in ways that cannot be captured by postcoordinate Boolean combinations or by word proximity searches that drop relational prepositions as stop words; (2) a vast network of linkages between LCSH headings and the Library of Congress classification scheme depends on precoordination; (3) displays of precoordinated strings enable researchers to simply recognize whole array of relevant research options that they could never specify in advance in postcoordinate combinations; and (4) the precoordination of terms is inseparably linked to a vast network of cross-references that would vanish without it. In the future, LCSH must serve in both the environments of online library catalogs and the World Wide Web, not the latter in place of the former. An Online Cataloging-in-Publication (OCIP) program would enable the library profession to maintain the necessary precoordination of LCSH headings in OPACs and also to insert librarian-created LCSH elements into the Web headers of participating online publishers. This would enable users to exploit the existing precoordination and postcoordination capacities of OPACs and also to exploit LCSH more extensively in the exclusively postcoordinate search environment of the Web. (Contains 25 references.) (MES)