The effect of atmospheric pollution on the growth of lichens has long been discussed. This work was aimed at obtaining data on the effect of such pollution, from the Iron and Steel works at Consett Co. Durham, on the lichen flora of the district. The degree of pollution found to the west of Consett was evaluated by analysis of lichen thallus for sulfur and from bark washings for amounts of deposited matter. These results were compared with standard pollution data at Consett, obtained from the DSIR, and a pollution gradient passing west from Consett was plotted. The distribution of corticolous, saxicolous and terricolous lichens in this area was mapped. The results from these distributions were applied to the pollution data and the control of lichens by pollution shown. The modification of the pollution effect by humidity factors is also discussed.