An attempt was made to desulphurise various types of coal, using as inocula enriched cultures from the bacteria adhering to each of the coal types, while the desulphurisation of the same coal types, inoculated with an indigenous culture derived from the drainage of a mine, was simultaneously monitored. The results demonstrate the convenience of using coal-derived inocula, with 70-90% of pyritic sulphur being removed, while chemical desulphurisation is of little significance with the majority of coal types. In reference to the Immediate Analysis of the coal, it should be stressed that this scarcely changed apart from the variations caused by acid attack; owing to that the ashes were partially eliminated and the treatment reduces the sulphur emission value. (C) 2001 Elsevier Science B.V. All rights reserved.