The oil fields of Burma lie in its central valley through which the Irrawaddy and its branch, the Chindwin, rivers flow. Mountain ranges flank the western side of the valley and the Shan plateau lies to the east of it. The valley is composed chiefly of Tertiary sediments with a few igneous rocks. The main structure is a syncline running near and parallel to its western margin. Approximately in the center of the valley between the main syncline and a parallel central volcanic belt lie the smaller anticlines of the main oil fields. In one of the fields natives have for centuries been digging for oil by hand. The first well completed by machinery, drilled by the Burmah Oil Company, was finished in 1889 and was only 727 feet deep. Other early wells were even shallower. The stratigraphy of individual formations is dealt with and nine oil fields are here described.