The BGS Geochemical Baseline Survey of the Environment (G-BASE) was the national strategic geochemical mapping programme in Great Britain. The project set out to establish the chemistry of the surface environment by the collection and analysis of stream sediment, stream water and soil samples. Beginning in the late 1960s in northern Scotland and moving southwards across the country, the primary focus was mineral exploration, however, the project quickly developed to address important environmental concerns. The final G-BASE samples were collected in southern England in 2014. The outputs from the G-BASE project provide an invaluable, systematic baseline of geochemical information for Great Britain, serving as a marker of the state of the environment against which to measure future change. The routine collection of regional soil samples was introduced in 1986 in areas of poor drainage density, with an average sample density of one site per 2 square kilometres. Urban soil sampling commenced in 1991, with an average density of four samples per square kilometres, for the urban areas of Belfast, Cardiff, Corby, Coventry, Derby, Doncaster, Glasgow, Hull, Ipswich, Leicester, Lincoln, Manchester, Mansfield, Northampton, Nottingham, Peterborough, Scunthorpe, Sheffield, Swansea, Stoke, Telford, Wolverhampton and York. Topsoil samples were collected between depths of 5 cm and 20 cm, and were sieved through a 2 mm mesh and milled to less than 150 microns. The data include XRF and direct-reading optical emission spectrometry (DR-OES) analyses for some or all of the following elements: Ag, As, Ba, Bi, Br, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, Hf, I, K, La, Mg, Mn, Mo, Nb, Ni, P, Pb, Rb, Sb, Sc, Se, Se, Sn, Sr, Ta, Te, Th, Ti, Tl, U, V, W, Y, Zn and Zr. Loss on Ignition (LOI) and pH (in a slurry of 0.01 M CaCl2) were also routinely determined on 50% of regional and all urban samples. For more information about accessing these samples and their analytical results, contact BGS Enquiries (enquries@bgs.ac.uk).