A textbook for the senior undergraduate or graduate student beginning a serious study of X-ray crystallography. It will be of interest both to those intending to become professional crystallographers and to those physicists, chemists, biologists, geologists, metallurgists and others who will use it as a tool in their research. All major aspects of crystallography are covered--the geometry of crystals and their symmetry, theoretical and practical aspects of diffracting X-rays by crystals and how the data may be analyzed to find the symmetry of the crystal and its structure. Includes recent advances such as the synchrotron as a source of X-rays, methods of solving structures from power data and the full range of techniques for solving structures from single-crystal data. Computer programs are provided for carrying out many operations of data-processing and solving crystal structures including by direct methods. These programs are required for many of the examples given at the end of each chapter but can be used to create new examples by which students can test themselves or each other.