Since his death in 1996, many scientific meetings have been dedicated to the memory of Paul Erdös. From July 4 to 11, 1999, the conference "Paul Erdös and his Mathematics" was held in Budapest, with the ambitious goal of showing the whole range of Erdös' work - a difficult task in view of Erdös' versatility and his broad scope of interest in mathematics. According to this goal, the topics of plenary lectures and parallel sections included number theory, combinatorics, analysis, set theory, probability, geometry and areas connecting them, like ergodic theory. The conference has contributed to changing the common view that Erdös worked only in combinatorics and combinatorial number theory. In the present two volumes, the editors have collected, besides some personal reminiscences by Erdös' old friends, mainly survey articles of a different nature: on his work, and on areas he initiated or worked in.