The results of a study of the indexing provided by the "Bibliography of Agriculture" and 15 related secondary services are described. The data elements used with printed citations and the indexing features of each service are described and compared. A methodology was developed to compare the terms provided by the Bibliography and each other service for the same citations. The percentages of related and unrelated term pairs (one term used by the "Bibliography of Agriculture" compared with one term used by the other service) were given for services which use multiple term indexing and for those which use single term indexing. The number of subject access points per citation provided by each service for the same source material was also determined and compared. The unique subject access points contributed by the Bibliography and each other service were measured. Other comparisons were made between the index terms used by the other services and the "Bibliography of Agriculture" subject index, the index term words assigned to an article, the words in the title of the article, and the subject headings used by the "Bibliography of Agriculture" and other services for the same citations. (Author/SG)