The conservation of historic monuments, sites and structures constitutes an inter-professional discipline co-ordinating a range of aesthetic historic, scientific and technical methods. Conservation is a rapidly developing field, which, by its true nature, is a multidisciplinary activity with experts respecting one another's contributions and combining to form an effective team. Conservation is an artistic activity aided by scientific and historical knowledge. Main topics at this Congress included: - the most appropriate methodology for the assessment of the degree of weathering of stone - development of new methods and instruments for the diagnosis of the state of conservation, for the study of alteration mechanisms and for conservation treatments. - the definition of Technical European Standard Methods for the evaluation of conservation treatments of artistic and historic stone objects and monuments.