Stone monuments represent an important part of our world’s cultural heritage. The awareness of increasing stone damage on monuments coupled with the danger of irretrievable loss of cultural heritage has resulted in great efforts worldwide for monument preservation. Meaningful damage diagnosis is required for comprehensive characterization, interpretation and rating of the stone damage. In situ investigation of monuments makes an important contribution to damage diagnosis on stone monuments. The monument mapping method is presented as an established non-destructive procedure for in situ studies on stone damage. It can be applied objectively and reproducible to all stone types and to all kinds of stone monuments. The consequent use of weathering forms, damage categories and damage indices for precise registration, documentation, quantitative evaluation and rating of stone damages is explained. It provides a modern contribution to improvement of scientific knowledge in the field of stone deterioration and it facilitates important information on the need, urgency and appropriate types of economic and sustainable monument preservation measures. Furthermore, it is very suitable for certification and control of preservation measures and for long-term survey and maintenance of stone monuments. The innovative evaluation strategy ‘weathering forms – damage categories – damage indices’ is based on a detailed classification scheme of weathering forms, that has been developed on the basis of investigation at numerous monuments worldwide considering different stone types and different environments. The methodological approach to systematic evaluation of stone damage – based on monument mapping – is described and practical applications are demonstrated by means of some case studies.