This coherent anthology presents the state of the art in the booming area of online algorithms and competitive analysis of such algorithms. The 17 papers are carefully revised and thoroughly improved versions of presentations given first during a Dagstuhl seminar in 1996. An overview by the volume editors introduces the area to the reader. The technical chapters are devoted to foundational and methodological issues for the design and analysis of various classes of online algorithms as well as to the detailed evaluation of algorithms for various activities in online processing, ranging from load balancing and scheduling to networking and financial problems. An outlook by the volume editors and a bibliography listing more than 750 references complete the work. The book is ideally suited for advanced courses and self-study in online algorithms. It is indispensable reading for researchers and professionals active in the area.