Abstract: We were assigned by the General Directorate of Mineral Research and Exploration Institute of Turkey to visit and study the Iranian oil fields.During our visit we have been, fortunate enough to see the oil fields of QumIn central Iran, Kermanshah in western Iran, Consortium oil fields in-southernIran, as well as the Caspian oil fields In northern Iran.Stratigraphical sequence In Iran ranges from Cambrian up to and including, Quaternary period. Fossiliferous Cambrian strata were seen In southwesternIran; they consisted of red and green colored shales, red sandstones and bituminous dolomites.Strata of pre-Devonian age were seen in the Elburz Mountains. In the northern, northwestern and central Iran fossiliferous strata of Devonian period consisted of red sandstones, shales and quartzites; In addition there were Fosulina-bearlng limestones, bituminous limestones and shales which are generallyregarded as of Permo-Carboniferous age.  Strata of Triassic period are varied in character; though generally occurring asdolomites and laminated limestones, they appear as massive limestones, dolomitesand calcareous shales in southwestern Iran, as gypsiferous red beds in southernIran and as sandstones, shales and coral limestones in southeastern Iran.Jurassic period is represented in general by bedded limestones, dolomites andmassif limestones. There are Carboniferous shale, sandstone and conglomerate intercalations in the Lower and Middle Jurassic epochs.Lower Cretaceous is generally represented by limestones, Upper Cretaceousstrata have flysch characteristics.Strata of Eocene-Oligocene epochs are generally marine in nature. In thesoutheast they arc dominantly flysch in character; on the other hand, in the southwest green and purple colored shales, sandstones and limestones are predominant.In central Iran, as well as in the Elburz Mountains, thick marine formations alternate with continental formations.Strata of Miocene age are found as red gypsiferous beds and sandstones intercalated with marine limestones and muddy limestones. Mio-Pliocene strata aregenerally found as elastics, partially of marine and partially of continental facies.Older Quaternary deposits are found as terraces and mainly consist of travertine and loess, Young Quaternary deposits are found as alluviums.Various igneous and metamorphic rocks of Precambrian, pre-Devonian,pre-Cretaceous and post-Eocene ages have been distributed throughout Iran. Inaddition, there are extrusive rocks of mainly Paleozoic and Plio-Quaternary ages,which are observable at various localities.In the Qum region of central Iran, there are two main oil structures: the Alborzstructure yields oil, while the Sarajeh structure yields natural gas. In both structures the reservoir rock is Qum formation of Oligo-Miocene age.In the Kermanshah region of western Iran two structures, the Napht-i Shahand Imam Hassan structures, are oil bearing. In the former, oil is found in theKalhor limestones of Oligo-Miocene age, while in the latter, oil is concentrated inlimestones of Turonian age and in muddy limestones of Cenomanian age.In the southern Iran Consortium area, only the Ahwaz, Agha Jari and KhargIsland oil structures have been visited. The reservoir rock in the Ahwaz and AghaJari structures is the Asmari limestone of Oligo-Miocene age. On the other hand,in Kharg Island structure, oil is found in Khami limestones of Lower Cretaceousage.In the Caspian Sea region exploration work is still under way; only one borehole yielded natural gas.Besides these geological studies, the refineries of Kermanshah and Abadanhave also been visited. Additionally, the best petroleum laboratories of the MiddleEast, Rey Depots in Teheran, were also seen. The first economic oil discovery in Iran was made in 1908 with the finding ofMasjid-i - Soleiman structure, Until 1951, all petroleum activities were conducted by the Anglo-Iranian Oil Company (at present, the B.P. Company Limited).In 1951 Iranian oil fields were nationalized and the present National IranianOil Company (NIOC) was established. With the exception of the Consortiumarea in the souths all oil fields of Iran are exploited only by National Iranian OilCompany. Since 1954, the petroleum activities in the southern area are carriedout by the Iranian Oil Exploration and Producing Company (Consortium).