Within the Maracaibo basin, northwest Venezuela, are exposed rocks ranging from pre-Cambrian to Recent time. The lithology, stratigraphic relationship, distribution, age, paleontology and correlation of the entire stratigraphic column are considered, but the petroliferous formations of the Cretaceous, Paleocene, Eocene, Oligocene and Miocene receive emphasis. The Merida range geanticline is the dominant structural feature of the region. Subordinate producing structures are discussed. The estimated reserves of the basin exceed 5,500,000,000 barrels. Includes an appendix by A. N. Dusenbury, Jr., on Venericardia toasensis Dusenbury n. sp. from the upper Paleocene on Toas island, Mara district, Zulia state.