It is concluded from the high correlation between visible transplant damage and SO₂ levels, that SO₂ pollution gradients can be sufficiently described by means of the lichen transplantation method. The transplanted lichen species should be chosenon the basis of its SO₂ sensitivity, this being neither too high nor too low in relation to the average SO₂ level of the area under investigation. A description of the existing lichen vegetation or a knowledge of the SO₂ variation in the area should thus precede any transplantation experiments. Hy-pogymnia physodes, which was also used successfully in transplantation experiments in Oslo (KROG & BRANDTH, 1975), showed sufficient variation in degree of damage after 6 months of transplantation in the Copenhagen area to be a useful indicator of SO₂ air pollution levels. Thus, our data suggest that Hypogymnia physodes is a suitable organism for use in future transplantation experiments on air pollution levels in metropolitan areas in southern Scandinavia.