As part of the work of modelling the thermal history of the Ediacaran (Late Neoproterozoic) and Early Cambrian sequences of the eastern Officer Basin that are hosts to oil shows and potential source and reservoir rocks, an essential prerequisite is to obtain reliable maturity data. Measurement of present-day maturity levels of target formations in strategically located drillholes across the basin then makes possible the determination of the timing of oil and gas generation in relation to trap formation. Previous studies by the senior author and his associates have exploited the capability of triaromatic hydrocarbon distributions to provide thermal maturity data on pre-Devonian sediments devoid of vitrinite phytoclasts. The aim of the present investigation was to augment the existing aromatic maturity database for the Officer Basin by undertaking measurements of methylphenanthrene index, methylphenanthrene ratio and calculated vitrinite reflectance on the triaromatic hydrocarbons extracted from another 10 mudstone samples. The new data proved consistent with those obtained previously from the same or adjacent drillholes, and indicate that the sediments sampled all lie within the conventional oil generation window.