This work investigated the vertical distribution and fractionation of uranium and thorium in soils under contrasting arable and woodland sites based on the same parent material. The effect of long-term application of phosphate fertilizer on U and Th concentrations in the arable soil was also assessed. The arable surface soils contained higher amounts of U compared with underlying layers and the woodland soil profile; by contrast, the Th distributions were very similar in both arable and woodland soils. The U and phosphate concentration profiles within the arable soil were broadly similar; U was strongly associated with Ca (r = 0.94) and soil P content (r = 0.86) whereas the U concentration profile in the woodland soil was virtually uniform with depth. The ‘excess’ U in arable soil, associated with long term P fertilizer application, was approximately 2.5 kg ha- 1 with 80% in the top 30 cm of the soil profile. A sequential extraction technique was used to fractionate U and discriminate between ‘reactive’ (non-residual) and ‘residual’ forms of U. The reactive U was adsorbed, mainly by organic matter and Fe-Mn oxides in the arable topsoil and there was a very strong relationship between reactive U and soil phosphate content in the arable soil (r = 0.99, P < 0.001). The ‘excess’ U accumulated in the arable topsoil was also considerably more reactive than the co-existing native U. Thus the reactive fraction of the excess U ranged from 29 to 42 % compared with 14 to 15 % reactivity of the native U. Thorium in both soils showed a very consistent, and low, reactivity down the soil profile at about 4% of total soil Th content (96% residual), bound almost completely to humus.