The following is submitted as a summary of the present knowledge of the distribution of thorium in the State of South Australia. The aim has been to assemble the information contained in the numerous departmental reports and to record the degree of investigation to which each occurrence has been subject. It is thus based almost entirely on work by a number of officers and is intended to be used as a basis for future exploration. No active field work has been done to test any conclusions that may be contained herein.