During a one-month period in the fall of 1987 a wide range in the visual quality of the atmosphere at Research Triangle Park, NC, was observed. During the period, the light scatter coefficient; SO2, NO2, and O3 concentrations; temperature; relative humidity; and radiation intensity of the atmosphere were continuously monitored. In addition, 60 filter samples were intermittently collected with two dichotomous (large and small particle) size-selective samplers. The dichotomous samplers were operated concurrently to obtain samples on Teflon and quartz filters for different analyses. Also collected were six impactor samples for sulfate size distribution analysis; and at selected times during the study, long-path measurements were made of the atmospheric extinction coefficient and the extinction of contrast by the atmosphere. (Copyright (c) 1991--Air & Waste Management Association.)