An atmospheric aerosol sampling analysis experiment at a site near the center of the New York metropolitan area was carried out to delineate relationships existing between degree of visibility and various aerosol characteristics in a polluted atmosphere. Size-fractionated and unfractionated particulate samples were collected at four discrete levels of visibility and analyzed for SO4(-2), NO3(-1), Cl(-1), NH4(+1), Pb, Fe, Mg, Zn and total mass. At all levels of visibility, bimodal or multimodal particle size distributions were observed for total mass and, in some cases, for individual components. Decreased visibility corresponded to increased particle mass concentration especially in the fine particle fraction (ranging in size from about 0.1 to 1.0 micrometer dia.). Increases in the proportion of particulate sulfate and, to a lesser extent, of nitrate, chloride, ammonium, and carbon were also associated with decreased visibility.