The Reconcavo Basin is located in the northeast of Brazil, and is part of the Reconcavo-Tucano-Jatoba rift system. In this basin the first commercial oilfield was discovered in Brazil about 70 years ago, and the basin still remains until today a producer of hydrocarbons. The hydrocarbon generation within source rocks is controlled mainly by thermal maturation and by the type of organic matter. These parameters can be studied through petrological and organic geochemical analyses. The objective of the present study is to characterize the organic matter in the Gomo Member source rocks to obtain information on the type, content of the organic matter, and thermal maturity. The Gomo Member is considered the main hydrocarbon source rock of the Reconcavo Basin. The Gomo strata is predominantly comprised of pelitic sediments and black shales, intercalated with thin layers of carbonates and fine-grained sandstone. Results obtained from the analyses of 37 cutting samples collected from six petroleum exploration wells indicate that these rocks have organic carbon contents >0.5 wt.%, however, the organic matter has a relatively low hydrocarbon generation potential as indicated by low S2 values. A plot of Hydrogen (HI) versus Oxygen Indices (01) indicates kerogen type II, suggesting terrestrial and lacustrine contribution to the organic matter. The Rock Eval parameter Tmax and vitrinite reflectance show that the majority of the samples are in the marginal to low mature and moderately mature stages of the oil generation window. Considering the geochemical and petrological parameters, it appears that the southern compartment of the Reconcavo Basin had the highest rate of accumulation and preservation of the organic matter, and consequently the highest petroleum generation potential. (C) 2010 Elsevier B.V. All rights reserved.