A general survey of the methodological and technical aspects of the maintenance of stone materials in buildings. The Normal standards published by the National Research Council and the Istituto centrale del restauro, have been taken as a base for definitions and technical solutions. Maintenance covers the diagnosis, including the study of the forms of deterioration, characterization of the materials and of the environment, and the conservation interventions such as cleaning, consolidation, gluing and filling, repair of mortars, substitution, and protection. Analysis, tests and surveys for diagnosis, the choice and the control of maintenance interventions are described.