Soil warming experiments were conducted in tundra heath and polar semi-desert soils at the High Arctic location of Ny-Alesund, West Spitsbergen, Svalbard, The warming treatment resulted in an 8-10% increase in the annual thermal budget for soil-dwelling oribatid mites (Crytptostigmata). Samples of the oribatid mite populations were taken during three summers using high gradient extractors, from warmed and control plots. Changes in population density were analysed for six species of oribatid mite. The oribatid mite fauna of these soils is well adapted to a wide temperature range and responds to short-term changes in the soil microclimate. there was little evidence from this three-year experiment that persistent above normal temperatures affected population growth rates.