An investigation on the effects of sonic waves to improve the efficiency of fine coal dewatering in vacuum filtration has been carried out. The objective was to study the synergistic effect of vacuum filtration and sonication in the presence of surface active agents and to understand the importance of the various process parameters to devise scale up criteria for industrial application. Under optimal conditions, the residual cake moisture was substantially decreased and filtration rate improved respectively, from 21 to 10% and 4.3 X 10(3) to 10.5 X 10(3) l/m(2)/h. It has been estimated that the oil cost saving could be as high as Rs 98 per tonne of dry solid. The cost benefit analysis has also been described and discussed.