ABC-V Symposium took place in the Vallarta Ballroom of CasaMagna Marriott Hotel in Puerto Vallarta, Mexico, during June 27th–July 1st 2005. The meeting followed the idea of the past international symposia held in Lyon 1984, in Sapporo 1988 and 1993, in Rolduc near Aachen 1998, and in Matsuyama 2001. These conferences focus on all topics related to solid acid–base chemistry, including catalyst synthesis, reaction mechanisms, characterization, kinetics, theory, industrial applications, and new directions in solid acid–base catalysis.

The Program consisted of 32 oral contributions, including 8 plenary and 6 invited lecturers, presented from researchers of USA (8), Japan (8), Europe (12) and Latin America (4). Besides, 63 contributions were presented in two poster sessions. About 150 delegates from 24 countries participated in this symposium, including scientists and engineers from industry, academia and research institutions. Contributions on acid catalysis were predominant, but about 40% of them focused on base, base–acid or bifunctional metal-base catalysts. The meeting provided ample opportunities for learning, discussion, and for personal interactions.

This special issue of Catalysis Today contains 21 selected contributions of ABC-V Symposium. Several papers on acid catalysis are fundamental studies on reaction mechanism, spectroscopic characterization, and intermediate formation predictions. Other papers deal with solid acid preparation, in particular with the development of novel strong acid catalysts. Six papers present fundamental and applied studies using base catalysts, in particular MgO-based catalysts. Two papers on acid and acid–base catalysis are presented by industry researchers, namely from Mitsubishi Chemical and Asahi-Kasei Corporation.

Acknowledgements for the organization work should be addressed to the Organizing Committee led by Stuart Soled and Jose Santiesteban (Exxon Mobil), and John Byrne (Engelhard Corporation). The excellent scientific program would not have been possible without the generous financial support by Exxon Mobil, Sumitomo Chemical, Dow, Rohm and Haas, Bayer, ChevronTexaco, and Professor Tanabe.

The successful scientific achievement of this Symposium stimulated the Advisory Board members to continue with the organization of ABC meetings. It was decided that ABC-VI Conference will be taken place in Europe, in 2009. The Tanabe Prize for Acid and Base Catalysis will be awarded for the first time at ABC-VI, and then to each subsequent ABC meeting.

The manuscripts in this volume were reviewed by experts and followed by the author's revisions to incorporate their suggestions. We would like to thank all the authors who worked diligently to prepare their manuscripts, and are indebted to the reviewers for the numerous valuable suggestions to improve the scientific quality of these manuscripts. We hope that the material presented will be the value for scientific and technical community and will stimulate more investigation and new ideas.