An intermediate lexicon is described that employs a technique which allows, for a given subject area, the automatic translation of subject indexing from one indexing scheme into another. The lexicon was structured according to the principles of faceted classification and contained approximately 1,000 entries covering the field of library and information science. A number of tests were undertaken to determine the effect on the switching performance of the intermediate lexicon of varying the relative vocabulary size, structure, and mode of use of the pair of indexing schemes between which the lexicon is used as a translation device. Inter-indexer consistency was also considered. Results showed that the greater the relative specificity and vocabulary size of the input language the better the switching performance. Performance was good also for the switch between the two classification schemes used in precoordinate mode. Factors in the input language which adversely affected the performance were low specificity and the frequent use, in thesauri, of coordination to represent concepts. (Author/LS)