[en] The main objective of the survey was to establish the radionuclide content of permanent pasture soils. The extent of contamination from the Chernobyl accident was also studied with the use of Cs-134 as an indicator of Chernobyl fallout. A preliminary radiological assessment was performed by referring to the generalised derived limits. Results of the grassland grid survey show that Chernobyl-derived radiocaesium was widely spread throughout Northern Ireland with the exception of the East Coast where the deposition was more localised reflecting the showery-rainfall pattern on the 3rd May 1986. Accumulation of Chernobyl material showed a high correlation with rainfall on that day, which resulted in a substantial increase in Cs-137 levels compared to estimated pre-Chernobyl concentrations in many areas. The main areas affected lay in a band across the country from the North East to the South with a smaller incursion to the North. The plutonium content in soils from Northern Ireland arising from nuclear weapons fallout was similar to levels found in other surveys completed in Great Britain before Chernobyl. (author)