The I.A.P.(Index of Atmospheric Purity) by the distribution of Bryophtes on the bark of various latifoliate tree trunks was investigated at four sites(Daeheung, Songkwang, Jeungsim, and Heunggook Temple) from April, 1991 to April, 1993. The IAP was in inverse proportion to the degree of air pollution. The I.A.P at four sites were estimated 78.2 at Daeheung temple, 61.0 at Songkwang temple, 28.3 at Jeungsim temple, and 10.3 at Heunggook temple, respectively. The distribution degree of Bryophytes in Heunggook temple progressed during the last ten years. It represents the bettrment of air quality. Bioassay by means of lichens seems to have great potential for better and less expensive ways of measuring pollution levels instead of the high cost of buying and maintaining air pollution monitoring equipment.