Microbial desulphurization of coal using a pyrite oxidizing organism Such as Thiobacillus ferrooxidans, results in approximately 90% pyritic sulphur reduction in 30 d. An integrated technique. comprised of bacterial preconditioning and subsequent oil agglomeration, is concerned with surface modification of the pyrite by short contacts (2-240 min) with a culture of Thiobacillus ferrooxidans and its rejection during agglomeration. Coal (-250 mu m) was preconditioned with the bacterial culture for 2.5-30 min before subjecting it to oil agglomeration. About 75-80% ash rejection and 90-97% pyritic sulphur reduction (PSRD) have been obtained. Extending preconditioning for 240 min could not improve the PSRD beyond 97%. By increasing the particle size from -250 mu m to -800 + 400 mu m the pyritic sulphur reduction (PSRD) decreased from 97% to 71%, whereas prolonging the preconditioning period to 240 min enhanced the PSRD to 90%. The integrated technique has considerably reduced the time requirement from 20-30 d to 30-240 min in order to obtain 90% pyritic sulphur reduction. Castor oil has been used as the agglomerant and found to be a good substitute to traditionally used petroleum fractions.