International Tables for Crystallography is the definitive resource and reference work for crystallography and structural science. Volume A of the series, Space-group symmetry, contains diagrams and tables of data for the 17 plane groups, the 230 space groups and the 32 crystallographic point groups.This new edition is edited by M. I. Aroyo and has been extensively updated and revised. Part 1 of the volume provides an introduction to space-group symmetry. It includes chapters on groups, crystallographic and space-group symmetry, descriptions of space groups, coordinate-system transformations and methods of space-group determination. The final chapter provides a useful introduction to topics treated in more depth in Volumes A1 and E of the series. The chapters in this part have been written with teaching in mind, and will prove invaluable for undergraduates or graduates wishing to learn about symmetry in crystallography, while providing a clear introduction to the topic for researchers from other disciplines. Part 2 of the volume presents the diagrams and tables of plane- and space-group data. The layout of the tables of data, the symbols used in the diagrams and the classification of the space groups are explained in a useful guide. Together these form an essential resource not only for professional crystallographers, but also for chemists, physicists, mineralogists, biologists and material scientists who employ crystallographic methods and who are concerned with the structure and the properties of crystalline materials. Part 3 treats more advanced topics on space-group symmetry, and covers crystal lattices, point groups and crystal classes, space-group symbols and their use, lattice complexes, normalizers of space groups, and magnetic subperiodic groups and magnetic space groups. There are eight new chapters in this 6th edition of Volume A, and five chapters have been revised. The layout of the space-group tables has been simplified as the sub- and supergroup data are now available in Volume A1, and there are new general-position diagrams for the cubic space groups. Additional diagrams showing tilted, perspective views of some of the more complex cubic space groups are also provided. More information on the series can be found at: http://it.iucr.org