This is the third edition of International Tables for Crystallography Volume C. The purpose of this volume is to provide the mathematical, physical and chemical information needed for experimental studies in structural crystallography. It covers all aspects of experimental techniques, using all three principal radiation types, from the selection and mounting of crystals and production of radiation, through data collection and analysis, to the interpretation of results. As such, it is an essential source of information for all workers using crystallographic techniques in physics, chemistry, metallurgy, earth sciences and molecular biology.

Volume C of International Tables for Crystallography is one of the many legacies to crystallographers of the late Professor A. J. C. Wilson, whose death on 1 July 1995 left the preparation of a revised and expanded second edition unfinished. When I was appointed as Professor Wilson's successor as Editor, I realised that although most of the material in the first edition was new, some had been carried over from Volumes II, III, and IV of the earlier series International Tables for X-ray Crystallography and had become outdated. Moreover, many of the topics covered were changing very rapidly, so needed to be brought up to date. In fact, by the time the second edition was published in 1999, more than half the chapters had been revised or updated and two completely new chapters, on reflectometry and neutron topography, had been included. The second edition of Volume C was also the first volume of International Tables to be produced entirely electronically.

The authors of the second edition were asked if they wished to submit revisions to their articles for this third edition in August 2001. All revisions were received within the following year. In total, 11 chapters have been revised, corrected or updated, and all known errors in the second edition have been corrected. I hope few new errors have been introduced. I thank all authors, especially those who have submitted revisions, and I particularly thank the Editorial staff in Chester for their continued dilligence.