In this study, geographically weighted summary statistics (GWSSs) are used to investigate spatial variation and spatial relationships in a freshwater acidification critical load data set covering Great Britain. This use of GWSSs not only provides valuable insight into the critical load process prior to a geographically weighted regression (GWR) calibration, but also helps in interpreting its output. GWSSs are similarly useful prior to the calibration of other spatial models, such as those used in geostatistics. Results agree with those of previous research, where relationships between critical load and contextual catchment data can vary across space. However the more sophisticated models used here are shown to be much more flexible and informative, allowing more spatial patterns to be revealed than before. (C) 2009 Elsevier Ltd. All rights reserved.