Dry samples of torbanite and soft brown coal, from which mineral matter and material soluble in chloroform have been removed, have been artificially matured in an attempt to simulate conditions in a subsiding sedimentary basin with a constant geothermal gradient. Sealed tubes were increased in temperature by 1°C per week beginning at 100°C. A tube containing each source material was opened and analysed at yearly intervals for six years. Olefins and carbon monoxide were not significant products at any stage. At less than 300°C torbanite generated a paraffinic crude oil in 35% yield, while the brown coal gave a wet, CO 2-rich natural gas. In most respects, these experiments, which are possibly as slow as can be realistically planned within a human time-scale, appear to have duplicated geochemical hydrocarbon generation.