Background Bacterial leaching has been shown to be possible in a number of instances for the recovery of metal values from ores. Most of the published literature refers to laboratory experimentation but it is fairly evident that bacteria have a beneficial effect on many leaching operations. The use of bacteria in leaching is envisaged to apply to materials of low metal content where liquors can be recycled through the mass and be subjected to an intermediate stripping stage for recovery of the valuable component. The major South Australian deposits of manganese are low-grade and fairly remote. Hence a cheap extraction process which could give a high grade manganese product would have an important effect on the economics of exploitation. Object Manganese has been leached elsewhere using bacteria and an investigation was undertaken to apply these established techniques on Pernatty Lagoon manganese to assess the feasibility of such a process. Summary of Results A sample of ore containing 22.9% Mn from Pernatty Lagoon was subjected to cultures of bacteria developed from mine waters from Pernatty and from a culture used for the same purpose by the US Bureau of Mines, under conditions described by the Bureau. Some slight evidence of leaching was obtained but results were neither consistent nor approached extraction rates obtained by the US Bureau of Mines. Conclusions and Recommendations It was concluded that the ore was not amenable to bacterial leaching under the conditions investigated. At this stage when work on the project stopped it became known that similar investigations were about to commence at the University of NSW and it is recommended that further work be deferred until better knowledge is available as to the best type of bacteria to use and optimum conditions for leaching. Contacts with Professor Ralph (University of N.S.W) has been made, and a friendly relationship established.