Coal from North Eastern Coal Fields of Tinsukia District of Assam was used in tests for bacterial desulphurisation with and without chemical treatment. The coal with 5.5 wt% of total sulphur was treated with aqueous NH4OH and Na2CO3. The pretreated coal was used for bacterial leaching with a mixed culture of Thiobacillus. Under various conditions of bioleaching, desulphurisation was better for the pretreated coal samples (namely 35-38 wt%) than for the raw coal (namely 5-27 wt%). However, the major component (organic sulphur) of the total sulphur could not be removed. The kinetics indicate the desulphurisation rate for pretreated coal to be higher than that for the untreated coal.