Rundle shale and rundle kerogen were reacted under hydrous pyrolysis conditions and the formed amounts of CO2 and carboxylic acids were measured. The amount of CO2 formed from kerogen when the shale is reacted exceeds that formed when the isolated kerogen is reacted, demonstrating involvement of the mineral phase in the reaction. The chemical composition of the kerogen is known from Siskin's work. It is possible that the CO2 formed during the reaction of kerogen (no mineral except pyrite) at 325 degrees C comes entirely from the kerogen. This is not true when the shale is reacted. For the reaction of kerogen at 350 degrees C, it is unlikely that all of the oxygen in the CO2 and carboxylic acid products is derived from the kerogen. When the kerogen was further demineralized with CrCl2, the amount of CO2 formed decreased. When a mixture of FeS, FeS2, and Fe2O3 was added to the kerogen, CO2 formation increased. Minerals play a role in hydrous pyrolysis reactions. It cannot be decided from these data whether this role is catalytic or direct involvement as a redox buffer.