This series of two consecutive special issues presents a selection of 21 expanded versions of papers presented during the SCAN-97 conference. SCAN-97 was held in Lyon, France, in September 1997, under the joint sponsorship of CNRS, GAMM, IMACS, École Normale Supérieure de Lyon, the city of Lyon and the French ministries of education and foreign affairs. The previous SCAN symposia have been held at Karlsruhe, Basel, Albena, Oldenburg, Vienna and Wuppertal. The next ones will be held at Budapest in 1998 (the address of the web page for SCAN-98 is http://www.inf.u-szeged.hu/ scan98/), and Karlsruhe in 2000. The SCAN meetings provide a forum for presentation of the latest research and developments in theory, algorithmic and arithmetic design for Validated Numerics; demonstration of new software available for Validated Numerics; reports of interesting case studies in industrial and scientific application of Validated Numerics; and discussion of new directions in research and development suggested by other advances in Scientific Computing.

I would like to thank the authors for their interest in the conference and the special issue, the referees for their timely and thorough work, and the editor in chief of JUCS, Professor Maurer, for having accepted to host these special issues.

Jean-Michel Muller