Site investigation and risk assessment have evolved into a major industry over the last two decades. The errors associated with sampling are now better documented, and any environmental consultant or site contractor needs to be well aware of the large differences which can result from poor site investigation design, and incorrect procedures on site, particularly with respect to sample selection, handling, transportation and storage. The assessment of potential contamination within a site is of critical importance for the future use of the site, predicting the cost of possible remediation, and the re-sale value. One of the main drivers for site investigation is SPOSH - ‘the significant possibility of significant harm’ being caused by the presence of contamination on the site. The design of a site investigation involves a great deal of research, and is generally referred to as the Desk Study, or a Phase 1 investigation. This will involve gaining information with respect to previous use of the site, locations of buildings (past and present), location of storage depots (particularly fuel tanks), identification of particular chemicals, feedstocks, and final products likely to have been stored on the site, and the possible discharge/spillages/burial of any materials, including waste generated on the site. In addition, the geology, hydrogeology, topography, location of natural water courses, and the presence of aquifers all need to be considered in assessing the potential mobility of any contaminants identified on the site. The sampling of the soil (natural ground and made ground) will need to reflect all of these considerations with respect to location, depth horizons, frequency, sampling grid pattern, etc. The errors associated with sampling on site are much greater than the analytical errors measured within the laboratory. Soil is an incredibly diverse and complex matrix. The chemistry of soil varies from the relative simplicity of calcium carbonate in chalky soils and silica in sandy soils, to complex clay minerals, and multiple variations in between. In addition, there is a huge range of potential contaminants, from household waste, builders’ rubble, industrial waste, paper, tar and concrete, through to highly toxic materials such as phenolics, explosives, cyanide and mercury. From the laboratory’s perspective, soil presents a series of problems in terms of the homogenisation and pre-treatment of the sample, all of which can impact significantly on the final analytical result.