A brief historical account of the background leading to the publication of the first four editions of the World Directory of Crystallographers was presented by G. Boom in his preface to the Fourth Edition, published late in 1971. That edition was produced by traditional typesetting methods from compilations of biographical data prepared by national Sub-Editors. The major effort required to produce a directory by manual methods provided the impetus to use computer techniques for the Fifth Edition. The account of the production of the first computer assisted Directory was described by S.C. Abrahams in the preface of the Fifth Edition. Computer composition, which required a machine readable data base, offered several major advantages. The choice of typeface and range of characters was flexible. Corrections and additions to the data base were rapid and, once established, it was hoped updating for future editions would be simple and inexpensive. The data base was put to other Union uses, such as preparation of mailing labels and formulation of lists of crystallographers with specified common fields of interest. The Fifth Edition of the World Directory of Crystallographers was published in June of 1977, the Sixth in May of 1981. The Subject Indexes for the Fifth and Sixth Editions were printed in 1978 and 1981 respectively, both having a limited distribution.