The geology of the St. Vincent Gulf region is discussed with particular reference to the possibility of the accumulation of commercial deposits of petroleum or natural gas. Recent evidence has shown that thick successions of Cambrian marine rocks occur on Yorke Peninsula and Kangaroo Island and a moderate thickness of Tertiary rocks occur west of Adelaide and probably out under the waters of St. Vincent Gulf. Petroleum or natural gas traces have been discovered in Permian and Cambrian rocks on Yorke Peninsula and it is concluded that the petroleum prospects are sufficiently strong as to warrant further investigations here on Kangaroo Island and of the Tertiary of the St. Vincent Basin. Geophysical work, mapping and limited structure drilling are recommended as a first stop.