The main objective of this study was to reconstruct and analyze changes in the natural and climatic conditions in the Karelian Isthmus over the Holocene. Bottom sediment samples from Lake Medvedevskoye were taken in the spring 2012. The sediments were AMS dated, and the datings were found to embrace the Late Glacial period and the entire Holocene. The integrated treatment of the bottom sediments included lithological, LOI and chironomid analyses. Based on the results of chironomid analysis, four stratigraphic zones were distinguished, and the natural environments corresponding to these zones were reconstructed.