This book by Alban Caroe and his son Martin, first published in 1984, is now recognized as a classic of its kind. In it was distilled the accumulated wisdom of the Caroe firm from a century´s experience of involvement with the great buildings of the land, especially churches, along with a deep understanding of the impact of modern techniques of stone treatment. The book concentrates on the essential principles involved and their clear exposition, rather than taking refuge in the practicalities of particular treatments. The result is a text which not only deserves reprinting for a new generation to learn and profit from, but does not need revising. Instead a series of notes have been added, drawing the attention of readers to major recent developments in the field.