A comparison of the petrographic data for coals from various Indonesian Tertiary basins shows that the coals have similar compositions with vitrinite the dominant maceral group. A feature common to most of the coals is the abundance of secondary liptinite, especially exsudatinite but also fluorinite. The association of exsudatinite with oil, adjacent to, or within liptinite and vitrinite macerals, suggests that exsudatinite is an indicator of oil generation, but at an early stage. Exsudatinite is probably an intermediate product in the pathway vitrinite/liptinite --> oil. Organic matter referable to exsudatinite and/or bitumen is found in coals and elastic rocks from eastern Kalimantan. The petrographic properties of both are the same. It is suggested that, for consistency of terminology, where this material is found in coal it should be termed exsudatinite whereas where it is found in other rocks it should be termed bitumen.