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. Deep soil samples (also known as profile soil samples) were taken from depths of between 35 cm and 50 cm at densities of 1 sample per two square kilometres (rural / regional areas) and 4 samples per square kilometre (urban areas). The G-BASE profile soils were generally sieved to 150 microns before analysis and determined by XRF for some or all of: 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. Since 2003, for both regional and urban sampling, deep soil samples and shallow soil samples were routinely collected from the same sites, but only the shallow soil samples were submitted for chemical analysis. The deep soil samples were archived in the National Geoscience Data Centre. For more information about accessing these samples and their analytical results, contact BGS Enquiries (enquries@bgs.ac.uk).