A total of 231 normal male human subjects were exposed for 4 hr to air, ozone, nitrogen dioxide, or sulfur dioxide; to sulfuric acid, ammonium bisulfate, ammonium sulfate, or ammonium nitrate aerosols; or to mixtures of these gaseous and aerosol pollutants. Only one concentration of each pollutant was used. This study, therefore, represents a preliminary survey, intended to allow direct comparison of studies to plan future research. None of the aerosols alone, nitrogen dioxide or sulfur dioxide with aerosols produced significant effects. A distribution analysis of subject responsivity to ozone gave a normal distribution among subjects not exposed to ozone, and a distribution shifted to the right and skewed to the right among those exposed to ozone alone or in mixture, with no evidence of bimodal distribution of ozone sensitivity.