Recent work on the development of Synthesized User Based Terminology Index Languages (SUBTIL), i.e., index and query languages for information systems which employ vocabulary elicited from potential users of the system, is described in this paper. Following a brief review of the literature on thesaurus construction and index languages is a discussion of a proposed procedure for eliciting a common and significant indexing language from a user group. The role of a computer in the procedure is described. Preliminary tests of the procedure are then summarized and the functions performed by a set of computer programs for analyzing the results of vocabulary elicitation are reviewed. Some of the questions which remain to be answered regarding the utility of SUBTIL are outlined, and the potential advantages of the SUBTIL process are considered. A 12-item reference list accompanies the text. (Author/JL)