This project has advanced the techniques of fission track analysis as a means of reconstructing the thermal evolution of sedimentary basins so that the conditions and timing of hydrocarbon generation can be assessed. It has been shown that the annealing of fission tracks in apatite is a more complex process than previously thought. A new quantitative description of apatite annealing has been developed which enables realistic predictions to be made of the annealing effects obtained from different kinds of thermal histories over geological time. These compare closely with fission track length measurements obtained on samples from a variety of well understood geological environments. Application of the results of this research to the Cooper-Eromanga Basin indicates that the present high thermal gradients encoutered in this area are a relatively recent phenomenon with the implication that hydrocarbon generation has been accelerating in the past few million years.