This book is a record of the contents of the papers accepted by the Congress Committee for presentation at the Fourth International Congress of Cybernetics and Systems (Amsterdam, The Netherlands, 21-25 August 1978). Two hundred and forty-five papers from authors from thirty-three countries of all the five continents are included. The papers are presented in an abridged form in order to highlight the main themes and produce a book that is both readable and relatively inexpensive. It was felt that after the publication of the weighty and rather costly form of the Proceedings of the Third International Congress of Cybernetics and Systems held in Bucharest, Romania in 1975 (Modern Trends in Cybernetics and Systems, eds. Rose and Bilciu, W. O. G. S. c. and Springer-Verlag, 1977; 3 volumes about 3500 pages; $150), an abridged but comprehen sive version would be more acceptable to readers. It is worth noting that the full names and addresses of authors are given for each paper, and requests to authors for more information and even full-scale papers would produce a positive response. As a matter of interest, each paper carries, in addition, brief summaries. The papers are arranged in each section or symposium in the alphabetical order of authors' names; this is not necessarily the order of presentation at the Congress.