The effect of air pollutant emissions in the Indianapolis "Metropolitan area on the acidification of snow was studied. In the winter of 1979-80, several snowfall events were analyzed to determine the levels of acidity in precipitation. This study revealed that the Indianapolis Metropolitan area is contributing to the acidity of its snow. Samples collected near the city were more acidic than those in the outlying rural areas.The impact of meteorological elements, size specific atmospheric particle concentrations and total suspended particulates on prevailing visibility in the greater Indianapolis Metropolitan area was also studied. The most important factors which statistically contributed to decreased visibility were relative humidity, wind speed and total suspended particulates as measured by high volume sampling.