Phase diagrams for multicomponent alloy systems are fundamental to metallurgy and materials science in terms of the extraction of metals, their processing to marketable products and their end usage. The study of phase equilibria requires a thorough knowledge of the subject, and of thermodynamic relationships. For these reasons, pedagogic tools of high quality are necessary. Amongst all of the existing documents there is one which is really outstanding; it is the book Alloy Phase Equilibria written by Alan Prince (a founder member of the Materials Chemistry Committee) and published in 1966 by Elsevier. This book has long been out of print. It has been made available in its original form without re-editing, to provide the scientific community and students access to this precious document. This has been made available through the kind permission of both Mrs Sheila Prince and of the publisher Elsevier.