The Tunguska Region is situated in the northwest of the Siberian Platform and incorporates several large structural elements of different ages. These are the Vendian-Middle Paleozoic Kureyka Syneclise, Katanga Saddle, and lgarka-Keta Marginal Sag. The superimposed Tunguska Syneclise, which extends beyond the limits of the region, began to form in the Late Paleozoic. In turn, these major features are complicated by lower-order structures. The region borders on the West Siberian Plate in the west, the Baykit Anteclise and Angara-Lena Steppein to the south, and the Nepa-Botuoba and Anabar anteclises in the east. To the north, the Tunguska Region is bounded by the Mesozoic Yenisey-Khatanga Trough. The sedimentary-volcanogenic cover of the Tunguska Region is composed of Riphean, Vendian, Paleozoic and Mesozoic formations, in which trapp intrusions occur. The total thickness of the platform is 10 km. The Riphean deposits do not occur everywhere; they are composed of carbonate and clastic rocks. The Vendian deposits rest on the Riphean, and on crystalline basement rocks. Clastic rocks occur in the lower part and sulphate-carbonate rocks in the upper part of the Vendian section. There is a transitional Vendian-Cambrian sequence, conformably overlain by the Cambrian salt-carbonate section. The reefal build-ups found at the base of the Cambrian are the oldest known in the world. The overlying Ordovician, Silurian, Devonian, and Lower Carboniferous deposits comprise a multi-facies sulphate-carbonate sequence. Paleozoic section terminates beneath the Middle Carboniferous-Permian continental coal-measure sequence, unconformably overlying the eroded surface of the older rocks. The Mesozoic part of the section is composed of Lower Triassic formations, and comprises tuffs and basalts. A particular feature is the lack of structural expression within the Vendian- Lower Cambrian and Triassic sections. The intrusions cut the sedimentary cover into blocks of different sizes, and have had a major influence on all aspects of the petroleum potential of the sedimentary section. Riphean, Vendian, Vendian-Cambrian, Cambrian, Ordovician-Devonian and Permian-Triassic oil and gas-bearing complexes have been distinguished within the sedimentary cover of the Tunguska Region. Reservoirs and seals are found in each of them. Permeable beds are represented by carbonate and clastic rocks. Porosity may be primary, cavernous, or due to fracturing. The seals are composed of carbonate, evaporite-carbonate and argillaceous deposits. Traps may be structural, lithological or stratiglaphical. Several oil and gas fields have been discovered in the region: the Soba, Payga and Moktakon fields are the largest. They produce from Vendian clastic and Lower Cambrian carbonate reservoirs, in structural and lithological traps. In the section describing the geochemistry of hydrocarbon fluids, the methods used by Russian geochemists to evaluate petroleum potential are considered briefly. The assessment of hydrocarbon resources in the Tunguska Region uses a volumetric-genetic method. The quantities of oil, gas and condensate realized in the Riphean, Cambrian, Ordovician, Silurian and Permian source rocks are estimated. The results of these calculations are given in the form of hydrocarbon resource prediction maps.