Stratigraphical subdivision of the Pleistocene formations in the areas affected by the numerous glaciations is still rather complicated and contradictory in many cases. Interglacial sediments are of primary importance for the stratigraphical subdivision of this stratum. The palynological signature of Interglacial sediments has often been used for determination of their chronostratigraphical position. Interglacial organic sediments consisting of peat and sapropelite were intersected in eight boreholes in western Lithuania (19.50–34.5m bsl, 55°40′30″–55°41′47″N; 21°08′03″–21°10′17″E).Palynological record suggests the deposition of the investigated sediments during the Lateglacial and the first half of the Interglacial including climatic optimum. The spread of shrub–herb vegetation with the patchy occurrence of Betula and possibly Pinus during the Lateglacial was recorded. Deposition of silt and sand with low input of organic matter indicates rather severe climatic conditions. Betula and Pinus-dominated forest with presence of Larix were typical of the early beginning of the Interglacial. Deposition of sapropelite and peat indicates increasing organic input. Ongoing climatic amelioration coincided with the rapid development of a mixed forest with numerous broad-leaved trees, e.g. Ulmus, Quercus and Tilia during the first half of the Interglacial. Further changes of the vegetation structure indicate migration of Alnus and Picea that may have been related with increasing humidity. Sediments from Mardasavas section that contains a similar palynological record were 230 Th/U dated at 202.4+38.6/−22.9ka (TSD method) and 220.6=35.3/−20.5ka (L/L method) (Gaigalas, A., Arslanov, Kh.A., Maksimov, F.E., Kuznetsov, V.Yu., Chernov, S.B., 2007. Uranium-thorium isochron dating results of penultimate (Late Mid-Pleistocene) Interglacial in Lithuania from Mardasavas site. Geologija 57, 21–29).The reconstructed pattern of the flora structure, e.g. presence/absence and abundance of certain characteristic taxa suggest the deposition of the investigated sediments during the warm climatic interval that can be tentatively correlated with the first half of the Snaigupėlė (Lubavian, Uecker, Schöningen or Gorkinskij) Interglacial attributed to Late Middle Pleistocene or to Marine Isotope Stage 7 (MIS 7) of the North Atlantic pro rata.