Clean air and a pollution-free atmosphere are vital ingredients in the recipe for survival, but at the nucleus of life is water and life is dependent upon adequate supplies of pure, uncontaminated H2O. This does not only apply to human life and the government's recently passed legislation requiring UK drinking water to measure up to EEC purity standards by 1995, but also to animal and plant life, especially where water exists as their natural habitat. September 1983 signified the launch of the Surface Water Acidification Project (SWAP) by the learned societies of the United Kingdom, Norway and Sweden. Within the SWAP, palacolimnology was identified by the management committee as a key area of research to trace the history of acidification in these three countries and to evaluate various hypotheses about its cause. Dr Richard Battarbee (University College London) and Dr Ingemar Renberg (University of Umea) were asked to co-ordinate this major collaborative project involving scientists from all three countries. "Palacolimnology and Lake Acidification" represents the proceedings of a Royal Society discussion meeting held on 25th August 1989 that reports on the successful completion of the project. It includes papers on 210Pb dating and the palaeoecological evidence for lake acidification (from diatom, chrysophyte, cladoceran and chironomid analysis of lake sediments) and the sedimentary record of atmospheric contamination (from trace-metal, total sulphur, PAH, mineral magnetic and carboaceous particle analysis). A major section of the book is devoted to tests of the various lake acidification hypotheses involving natural processes, changes in land-use and land management (including afforestation) as well as acid deposition. The book also contains papers on case studies, on the atmospheric contamination record of an ombrotrophic peatland, comparisons between diatom-based and model-based pH reconstruction and keynote guest papers from Canada, the USA and Finland. A diatom/pH modern calibration data set of over 160 sites is a special feature of the overall project. It has been used to develop new methods of pH reconstruction and error estimation for diatom assemblages in sediment cores. The results of SWAP underline the extensive nature of surface water acidification in the three countries concerned and demonstrate that acid deposition (more commonly known as acid rain) is responsible for this widespread and growing problem. It remains clear that with the onset of the 1990s and what promises to be a decade dominated by environmental issues, the government and all contending parties will be under increased pressure from the electorate to listen to and act upon information supplied by scientists and environmental groups.