Bolshoi Lyakhov is one of the group of the New Siberian Islands in the Laptev Sea. The permafrost of the island is of an extremely low temperature regime, polygonal wedge ice being the most specific feature. The geomorphological level considered is a so-called edoma, presumably of late-Quaternary origin: polygonal ice wedges are more than 10 m wide and up to 25 m deep on this level, and about 1 m × 1.5 m on the peat bogs of Holocene age. Sixty-six samples of underground ice were taken on both surfaces. The macro-ion content was analyzed, i.e. Ca, Mg, Na, K, HCO3, Cl, SO4. A significant difference in ion content was found between the older and the younger ice. The late-Quaternary wedge ice is characterized by the predominance of Ca and HCO3, while the Holocene ice contains considerably higher proportions of Na and Cl. This may be attributed to different environmental conditions during wedge-ice growth: more continental in the late Quaternary and more maritime in the Holocene.