Accumulation of air pollutants such as SO₂ and HF, chlorophyll contents, wax concentrations in needle tissue and needle growth of Pinus thunbergii were studied to verify possibilities of bioindicators of air pollution in Yochon Industrial Complex from July to October, 1991. The concentrations of water-soluble sulfur and fluorine increased nearer to the pollution sources regardless of sampling time, but water-soluble sulfur varied little during investigation and fluorine accumulated more with the passage of time. Total chlorophyll contents decreased a little in the slightly polluted site but sharply in the heavily polluted site. The higher the pollution level was, the more decreased chloroform- extractable wax. Air pollution exposure inhibited needle growth of Pinus tbunbergii during the latter part of growth period. Water soluble sulfur, fluorine and wax concentrations in needle of Pinus thunbergii were rather wood sensitive indicators of susceptibility to ambient air pollution from early July to early October. Chlorophyll contents seemed to be able to be used as a bioindicator of air pollution in early stage of needle development and in the severely polluted area. In the meanwhile needle length must be used as a bioindicator in latter part of growing season.