Since 1976, the crystallographic work of Michael James has concentrated increasingly on enzymes and their specific inhibitors, with special emphasis on application of techniques of the highest accuracy. He has solved the structures of a number of proteolytic enzymes and of several macromolecular enzyme inhibitors, all in complexes with their target enzymes in addition to structures of the isolated inhibitors. In addition, crystallographic studies were made of the binding of small, specific enzyme inhibitors, such as the binding of pepstatin to the aspartyl proteases and of chloromethyl ketones to the serine proteases. James’s particular contribution has been towards the precision of structural results. His studies have used very accurate data at the highest resolution, usually better than 1.8 angstroms, and have employed the most critical refinement techniques, often breaking new ground. An important advance was made by the use of quantum-mechanically calculated electron density distributions in the refinement of protein structures. The impact on our understanding of enzyme catalysis, its activation and inhibition, of the role of water, and of protein evolution has been considerable.