Dr Max Perutz, together with John Kendrew, received the 1962 Nobel Prize for Chemistry for using X-ray crystallography to solve the first two protein structures: haemoglobin and myoglobin. This paved the way for the solution of more than 300 protein structures that have now been determined in atomic detail. But what is the practical value of this knowledge? Has it had any effect on medical research and practice? In this volume these questions are explored by explaining how the structure of biological macromolecules is determined, and how X-ray crystallographic studies have led to new insights into disease processes and opened new approaches to medical treatment.