This monograph gives a carefully worked out account of the most basic principles and applications of the theory of fixed points. Until now, a treatment of many of the discussed topics has been unavailable in book form. The presentation is self-contained and is accessible to a broad spectrum of readers, including mathematically oriented people interested in applications. The main text is complemented by numerous exercises, comments and a comprehenseive bibliography. Andrzej Granas studied in Warsaw and then Moscow, where he earned his doctorate in 1958 under Lazar Lusternik. Since 1958 he has held various research and teaching posts in Poland, Canada, and elsewhere. During the Spring of 1970 he occupied a special chair at the Collège de France. In the early nineties, Dr. Granas founded the journal Topological Methods of Nonlinear Analysis, and since 1992, he has served on the Editorial Board of the Zentralblatt. He is an honorary member of the Gdansk Scientific Society.