In 1971, System Development Corporation (SDC) performed a study of academic library consortia, under contract to the U. S. Office of Education. The purpose of the study was to collect extensive information on existing academic library consortia and to develop a set of guidelines for planning, developing, operating, and evaluating a library consortium. One product of the study was the "Directory of Academic Library Consortia", which is LI 004173. The decision to produce a supplement came out of a desire to identify and describe a wider range of groups that are participating in the growing movement toward library cooperation. The supplement project was designed to include a greater variety as well as a larger number of cooperating library groups. To this end, the criteria for inclusion were significantly relaxed. Three basic criteria for inclusion were used in the preparation of the supplement. Cooperatives that were included (1) were not included in the directory; (2) had at least one academic library member; and (3) were actively engaged in, or actively planning to engage in, cooperative library activities. This supplement provides 135 additional entries and contains title and state indexes. (Author/SJ)