The report covers field sampling and aerosol analyses of haze formation: its nature and origin. Field sampling was conducted in downtown Columbus during the latter half of July 1972, in New York City (Welfare Island) throughout August, and in Pomona, California, for 10 days in mid-November. The sampling involved continuous monitoring of the meteorological conditions and the gas-phase composition of the air concomitant with collecting aerosols and measuring visibility reduction due to light scattering. Samplers were equipped with size-fractionating devices which provided particle separation near 2 um diameter. An analytical sheme was developed for determining the organic features of aerosols. The scheme not only provides qualitative information but also numerical data. Inorganic analyses were performed on aerosols.