The Yenisei-Khatanga Region is situated at the northern margin of the Siberian Platform. It extends 1.100 km in a west-east direction and covers an area of about 335.000 sq km. It forms part of the North Siberian Lowland, between the Taymyr Hills in the north and the Putorana Plateau in the south. The Region corresponds to the Yenisei-Khatanga Basin, a northern marginal trough of the Siberian Platform, bounded by a large platform structure (the Tunguska Syneclise) to the south, and by the Taymyr fold-belt to the north; to the west, the basin merges with the West Siberian Plate. The basin contains important gas and gas-condensate accumulations in Jurassic-Cretaceous clastic sediments. Geological and geophysical investigations have mapped numerous prospects, and the drilling of about 200 exploration wells has resulted in the discovery of 13 fields, with reserves of commercial size, or from which flows at commercial rates have been obtained in tests. The basin fill consists of coal-bearing clastic sediments of Jurassic-Cretaceous age, deposited in environments ranging from continental to open-marine, and reaching a thickness of 7-8 km in the centre of the basin. These basin sediments are underlain by a sequence of typical platform sediments of Late Proterozoic-Paleozoic-Triassic age, which in turn rest on a Precambrian crystalline basement. Minor volcanogenic rocks occur in the Triassic section. The sediments of the Jurassic-Cretaceous basin are rich in organic matter of predominantly humic type, contained in numerous coal beds and carbonaceous shales, with the highest concentrations being found in the Middle Jurassic section. Sapropelic matter of mixed type is very subordinate in the Mesozoic source rocks; larger amounts probably existed in Paleozoic source rocks, and reached a high level of maturity, resulting in the additional generation of gaseous hydrocarbons. Reservoirs in all the fields and prospects are sandstones, under shale seals, and occur at various Jurassic and Lower Cretaceous levels. Gentle anticlines are the most common trap type. Faulting played a very subordinate role in trap formation. Nearly all the fields are of multi-pool type. Three of the fields discovered are actually producing. Annual production from these three fields reached 5 billion m(3) in 1991. Two additional fields are ready for development. A small gas refinery is in operation at Dudinka. Practically all of the product is supplied to the Norilsk mining and smelting complex. Although oil has been found, so far only as very subordinate fringes in two of the fields, it is believed that more significant amounts of oil may have accumulated elsewhere in the Yenisei-Khatanga Basin, under conditions comparable to those which characterize the oil accumulations recently discovered in the adjacent Pur-Tazov Region of West Siberia.