The aim of this study is to provide geochemical and petrological data to characterize coals and carbonaceous shales from western Venezuela in terms of both compositional and thermal maturity parameters. The samples, collected in outcrop, belong to the Paleocene Marcelina Formation, the Eocene-Oligocene Carbonera Formation, the Paleocene Orocue Group, and the Lower Miocene Cerro Pelado Formation. Geochemical results are based on total organic carbon (TOC) content, Rock-Eval pyrolysis and proximate analyses, whereas petrographic data include vitrinite reflectance (R-r), and maceral composition. Thermal evolution of all samples is low, varying from immature to early mature. Coals and carbonaceous shales from the Marcelina and Cerro Pelado Formations are humic, the former having larger amounts of inertinite. Nevertheless, both groups of samples are compositionally homogeneous. Samples from the Carbonera formation and Orocue Group show a great compositional scatter, varying from humic to sapropelic. Our geochemical profile for Marcelina formation coals allowed the detection of the first coalification jump, whereas the Cerro Pelado Formation profile shows an abrupt decrease of organic matter content toward the top of the studied interval. Results shown here confirm data from previous studies relative to the high oil-source rock potential of Carbonera Formation and Orocue Group coals and carbonaceous shales. (C) 2004 Elsevier B.V. All rights reserved.