New data on spreading, cryogenic structure and isotopic composition (δ18O n δD) of composite wedges in the Pleistocene (age more than 50 000 yrs BP) sand deposits in the Laptev Sea region have been presented. Thick sand deposits underlay Late Pleistocene ice complex and contain several stages of composite wedges. The transitions from composite wedges to polygonal ice wedges and contacts between composite wedges and under-lying ice complex wedges are described in profiles. The lightest isotopic composition has been determined for the Middle Pleistocene composite wedges and ice wedges at Bolshoy Lyakhovsky Island (mean values δ18O vary from -34,3 to -36,0 ‰ and δD from -258,2 to -280,8 ‰). The Late Pleistocene composite ice wedges at Cape Mamontov Klyk (Anabar-Olenyek interfluve) are characterized by a heavier isotopic composition (δ18O from -28,5 to -31,7 ‰ and δD from -222,4 to -245,4 ‰). The isotopic compositions of wedges indicate cold and dry climatic conditions of the period of their formation. The analysis of isotopic parameters of ice wedges and of composite wedges clearly shows their similarity. Recent formation conditions of composite wedges as well as their isotopic composition have been presented for Zemlya Bunge. © A.Yu. Dereviagin, V.V. Kunitsky, H. Meyer, 2007.