A significant proportion of important nature conservation sites in Britain are subject to rates of deposition of sulphur and/or nitrogen which may perturb their ecology. This paper reviews studies of some of the effects of such pollutants on woodlands, upland and lowland heaths, and freshwaters. The weight of evidence shows that acidic deposition is causing damage on many sites which receive statutory protection. Many affected communities occur in areas where critical loads for H+ and S are exceeded, and would remain so even after implementation of current targets for reducing pollution. Little can be done on site to prevent such damage; conservation interests will best be protected by consideration of ecological data in the formulation of strategies for major reductions in emissions.