The organic matter from two marine oil shales, El-Lajjun (Jordan) and Julia Creek (Queensland, Australia), has been extracted by the commonly used HCl-HF method and the resulting products compared with those obtained using the NaOH-HCl method, i.e. with initial strong alkali extraction. The elemental analyses on a dry ash-free basis of the solids obtained by the two methods were similar to each other and to that of the original oil shale. The Py-GC-MS TLCs were also similar for the kerogens obtained by the two methods and for the original oil shale, showing regular n-alkene/alkane series, as would be expected from the high atomic H/C ratio, and series of alkyl substituted thiophenes and benzothiophenes. The solid state 13C NMR spectra showed similar trends.. XPS showed depletion of the sulfur and oxidation near the surface and confirmed that some aliphatic sulfur was present.