This is the third edition of the Index of Crystallographic Supplies prepared on behalf of the International Union of Crystallography by its Commission on Crystallographic Apparatus. The first was compiled by Professor A. Guinier in 1956 and the second under the editorship of Dr. A. J. Rose in 1959. At that time, it was intended that publication of revised editions of the Index should be a continuing project of succeeding Commissions. However, with changing membership and other pressing activities, the preparation of the third edition has been dependent on the acquisition of a Commission member with appropriate experience and enthusiasm. The Commission is therefore fortunate that Professor R. Rudman, who has had considerable experience in the collation of information on crystallographic matters, has undertaken this task. He has been assisted by the advice of the members of the 1969-72 Commission, in particular that of a group which, during a meeting in Marseille, France, July 4-6, 1971 to discuss Commission affairs, went over the draft of the Index in close detail. These included S. C. Abrahams, U. W. Arndt and D. M. Kheiker. The information included in the Index was gathered from replies to a questionnaire which was sent to a wide range of manufacturers and suppliers throughout the world. It is not intended as complete and exhaustive but it should provide a convenient starting point for the location of the appropriate sources of equipment and materials of use to crystallographers.