[en] This study provides a numerical estimation of the development of permafrost and frozen ground at Olkiluoto, where an underground repository for spent nuclear fuel is being designed at a depth of 420 metres. Calculations are carried out in 1-D for a 10 000 metres deep subsurface model using Olkiluoto's site-specific data. The time histories of ground level temperatures, ice sheet thickness, shoreline migration and vegetation covers effects are considered for two climate scenarios, Weichselian-R and Emissions-M. The model also includes the effects of decay heat from the spent fuel. Results are presented for the next 125 000 years for the Weichselian-R scenario and 200 000 years for the Emissions-M scenario. This study shows that in both Weichselian-R and Emissions-M scenarios the depth of the permafrost and frozen ground stays well above the repository level. The maximum permafrost depth is about 170 metres in the Weichselian-R scenario and 80 metres in the Emissions-M scenario. The depth of frozen ground is from a few metres to some twenty metres shallower than the permafrost depth, except during the glacial periods with warm-based ice-sheets when the subglacial permafrost remains completely unfrozen due to high water pressures induced by the ice load. (orig.)