The Ninth Prague Conference on Information Theory, Statistical Decision Functions, and Random Processes was organized by the Institute of Information Theory and Automation of the Czechoslovak Academy of Sciences from June 28 to July 2, 1982. Similarly as the preceding Prague Conferences, during their twenty six years histo ry, it provided a space for the presentation and discussion of recent scientific results, as well as for personal contacts of many scien tists both from abroad and from Czechoslovakia. Nearly 150 special ists from 17 countries participated in the Conference and they read more than 100 papers (including 18 invited ones), 88 of which have been published in the present two volumes of the Transactions of the Conference. Namely invited papers, having been read by outstanding specialists, have brought invaluable offer for participants to create themselves an orientation in the modern trends of the above mention ed scientific branches. Allow us to use this opportunity to express our sincere thanks to all who have contributed to the success of the Conference, espe cially to those who prepared and presented papers. Our gratitude is also due to Academician Jaroslav Kozesnik, the scientific editor of the Transactions, and to the editorial board for reviewing all papers and fulfilling many printing manage ment duties. We would like to appreciate a great work of all colleagues from the Institute of Information Theory and Automation, who participated in the preparation and in the organization of the Conference.