The gradual and progressive soiling of structures exposed to the atmosphere is commonplace. Material soiling results from the deposition of atmospheric aerosols. Both wet and dry deposition occurs. The particle size and the orientation, exposure and roughness of the surface determine the dominant deposition mechanisms. Wet deposition is not an important cause of surface soiling, but precipitation removes particles from a surface. Aged atmospheric particles are characterized by a bimodal size distribution of coarse and fine particles. Coarse particles tend to be inactive chemically and are removed by washout and runoff. A primary cause of building soiling in urban areas has been attributed to the fine-particle mode. When fine particles contain carbon they tend to be black, and adhere more tenaciously to surface than do course particles. Elemental carbon is usually 10-20 percent of the urban fine aerosol mass, and vehicular emissions, particularly diesel emissions, are the major source of urban black smoke. The soiling of buildings occurs over the years from fine particle deposition and is associated with low atmospheric concentrations. This paper describes the influences of particle size and rainfall on the deposition, and on the soiling of surfaces with different surface glosses, orientations and exposures.