Abstract: Favorable oil and gas geological conditions occur in the Persian Gulf Basin. There are three main source rocks, i.e. the Silurian, Jurassic and Cretaceous. All the three sets of source rocks are deposited in an intra-shelf basin during the time of transgression. The Silurian source rock is the hot shale of the Qusaiba Member with very high GR and TOC. This hot shale, which is highly matured and/or over matured, is distributed in the whole region of Mid-East discontinuously. The Jurassic source rock is bituminous limestone and black shale of mid-upper Jurassic with high TOC. Three source kitchens are developed in Jurassic. The Jurassic source rock is still remained in oil window, with a few in gas window locally. Cretaceous source rock is the mudstone in the Kazhdumi, Balambo, and Sulaiy Formations with high TOC. It is developed mainly in the Zagros fold belt and the NW Persian Gulf, and is oil matured. According to the research made previously, source rocks have notable control on oil and gas accumulations. The distribution of source kitchens controls the spatial distribution of oil and gas accumulation in each petroleum system. The maturity of source rocks controls the type of liquid, either oil or gas.