A synthesis of all the studies and research carried out on the very extensive subject of stone decay. The work is divided into the following major chapters: A. Stone weathering, B. The relationship between pollution and the deterioration of stone, C. Conservation, D. Products for the treatment of stone, E. The degradation of synthetic resins used in conservation. Chapter B on atmospheric pollution occupies a central place: it highlights the way in which decay in stone monuments is accelerated in urban areas and tries to explain the process whereby a pollutant is transformed in the atmosphere and its effect when it reaches the stone surface. Subsequent chapters contain advice on carrying out restoration work, describing the order in which remedial measures should be applied: diagnosis, cleaning, pre-consolidation, consolidation. The various protection and consolidation products to be used are also analyzed. A final chapter on the degradation of synthetic resins places users on their guard concerning the non-static characteristics and the long-term evolution of these products.