Adam Mrózek, professor of computer sciences at the Institute of Theoretical and Applied Informatics of the Polish Academy of Sciences in Gliwice, Poland, died on 26 August, 1999. With his passing the Polish science as well as the international rough set community have lost a great scientist. Born on 3 February 1948 in Zywieckie District, where later he received his secondary education in a renowned gymnasium. Having completed university education in 1970 at the Silesian University of Technology in Gliwice, he began uninterrupted scientific work of long standing in the Polish Academy of Sciences (PAS) in a department, which among the others due to his efforts, was transformed and currently functions as Institute of Theoretical and Applied Informatics (ITAI). He received all scientific degrees and titles from ITAI PAS in Gliwice. He served as the vice-director for scientific issues in this institute. He was active in his work till the last day of his life. The main aim of his scientific work was the desire to develop modern domains of technology and economy of our country, by means of most prospective and promising technical science branches' progress. His scientific activities were focused on the development of computers and computer systems, in particular their software, in a way that they might support human beings as much as possible. Namely, they might help monitoring technological processes' course, recognizing situations and decision taking, as well as helping human creative work. He was one of the pioneers of national programs of computerization of fundamental technological processes, computer methods for recognizing and decision taking, and helping human creative work that were carried by Institute of Theoretical and Applied Informatics. Thanks to his activities he was acquainted with the specificity of management processes in organizations, as well as technological processes in chemical, metallurgical, mining, glazier's, cement and even shipyard industries. While learning about them he gradually gained admiration and appreciation for the experience of those processes' operators. Thus, his main research objective was to formalize the operator's knowledge and experience in order to allow their application in computers and computer systems. His interests and activities resulted in many elaborations on human reasoning model, decision tables' creation and possibilities that fuzzy sets contribute to. The applications of rough sets theory were of particular interest to him and thus he devoted to them much of his attention. As a result, a book in that field of his co-authorship was published in 1999. He published many scientific articles in major international journals and books. His live finished much too early, but has resulted in rich fruits. We will gratefully remember him.