An experimental study of the influence of surface active agents on the dewatering of fine coal was undertaken with a view to evaluating the usefulness of such materials in reducing the residual moisture contents of filter cakes. Experimental evidence is presented which suggests that while polymeric fiocculants have a beneficial effect on settling, they can have adverse effects on the filtration of the thickened underflow. Detergent addition, on the other hand, was shown to reduce filter cake moisture, and the magnitude of this effect was determined, in part, by the prevailing electrochemical equilibrium at the solid-solution interface.