Our study aims to look for testate amobae (TA) in the surface and fossil sediments from the Cape Mamontov Klyk (73°60′-73°63′ N, 116°88′-117°18′ E), southern coast of the Laptev Sea, ca 150 km west of the Lena Delta and to discuss the potential of TA analysis for Glacial/Interglacial environmental reconstructions in Arctic Siberia. The radiocarbon age determination suggests that the studied sediments accumulated between ca 45,000 14C yr BP and present. A total of 98 TA taxa were identified in the 10 recent surface and 59 fossil samples. Results of taxonomical identification and ecological analysis of TA in the modern and fossil samples suggest that major changes in the soil moisture conditions took place. Our results show that soil-living taxa dominated the TA assemblages at the study sites during the past 45,000 years. The environmental conditions of the study area were most favourable (relatively warm and humid) during the Kargin Interstadial (ca 45,000-25,000 14C yr BP). An opposite situation is reconstructed for the Sartan Stadial (ca. 25,000-15,000 14C yr BP). During the Kargin Interstadial, optimum conditions occurred between ca 44,000 and 40,000 14C yr BP characterised by highest TA abundances and taxa diversity. This initial optimal phase was followed by the interval with drier and colder conditions about 40,000-30,000 14C yr BP. The sediments dated between ca. 24,000 and 18,000 14C yr BP show low TA abundances and diversity, in agreement with the much colder and drier environments during the maximum phase of the Last Glacial. The onset of the Holocene is indicated by a broad representation of obligate hydrophilic taxa, especially from genus Difflugia, suggesting wet and relatively warm conditions. By comparison with other environmental proxies used in the studied sections as well as from the neighbouring arctic regions our results suggest that TA analysis can provide valuable information, contributing to the better understanding of the Late Quaternary climate and environments in Arctic Siberia. © 2008 Elsevier B.V. All rights reserved.