Particulate matter deposited from atmospheric aerosols during a thirteen week study in Elizabeth, N.J. was examined in an attempt to identify the portion of the aerosol primarily responsible for soiling degradation. White painted panels were exposed to the atmosphere in sheltered and in unsheltered locations, and oriented horizontally and vertically in each. The reflectivities of all panels to visible light were measured weekly as a measure of soiling. In addition, TSP, fine aerosol fraction and coarse aerosol fraction were measured each week. The number and size distribution of the particles deposited on the panels were determined by the examination of scanning electron micrographs. The results show that the fine particles deposit in greatest number, but the coarse particles have the largest effect on area coverage. Large particles are present in lesser amount on the unsheltered horizontal panels, but fine particles in essentially the same amount on both horizontal panels. It appears that rain removes the coarse particles.