The Ardjuna Basin of northwest Java is typical of many Tertiary basins in that it contains high-wax crude oil. Pyrolysis-gas chromatography revealed that potential precursors of long chain (waxy) paraffins are present in coals of the Talang AKar formation, and are most abundant in those that are rich in “matrix liptinite”. Conversely, it was not possible to estimate waxy oil-generating potential using Rock Eval because pyrolysates from Talang Akar coal are mainly comprised of napthenic and aromatic compounds, these being derived from resinite and “fluorescing vitrinite”. Because of a controlling influence by the abundance of these macerals, changes in Hydrogen Index could not be used to assess maturity. Resinite and related macerals might play an especially important role in petroleum expulsion, as evidenced by their high genetic potential and, hence, inherent capability of saturating the source rock pore system. It is speculated that their maturation products, while not constituting “typical” crude oil, might pervade the coal fabric, deactivate adsorptive sites and hence facilitate the expulsion of waxy oil that is generated from matrix liptinite.