Describes objectives, research program, and preliminary results of an investigation into the influence of atmospheric pollution on the degradation of natural stone buildings in situ, in which several organizations, including Swiss, collaborate. The rate of accumulation of airborne sulfur is measured on several types of natural stone at a number of highly different locations both in Switzerland and abroad, in order to establish a correlation between rate of accumulation and level of pollution. It is planned to evaluate also the quantity of rainborne sulfurous compounds which can reach the surface of buildings. Experimental results obtained so far on the same type of stone show large variations of the amount of accumulated sulfur measured, depending on location and on the characteristics of the individual site.