It is now recognised that a multi-pollutant, multi-effect approach needs to be adopted to address the range of problems caused by atmospheric pollution. In this paper we use a relatively simple trajectory model (HARM) to explore the coupled behaviour of sulphur dioxide (SO₂), oxides of nitrogen (NO(χ)) and ammonia (NH₃) and the possible effects of future reductions in emissions of these pollutants on depositions of S and N across Great Britain. The performance of HARM with respect to concentrations and depositions of NO(γ) and NH(χ) is assessed by comparison with data from national monitoring networks. A range of emissions scenarios are modelled and the effects of these reductions on critical loads exceedance are explored using the critical loads function (CLF), which allows both the acidification and eutrophication effects of S and N deposition to be explored simultaneously. Spatial variations in the reductions of deposition of S and/or N required to meet critical loads are described. Reductions in emissions of the precursors of strong acids (SO₂ and NO(χ)) yield benefits in terms of ammonium deposition as a result of their coupled chemistry. The development of strategies to control nitrogen deposition will need to take this non-linearity in to account.