The fundamental principles governing the filtration of fine (nominally -0.5 mm) coal are not well understood. This has recently been recognised by the Australian coal industry as a major hurdle to significantly improving dewatering technology and performance. This study quantifies and compares the respective influences of filter cake microstructure, and coal surface and bulk properties on the vacuum filtration of fine bituminous coal slurries. It is shown that filter cake microstructure is the dominant factor, particularly in determining the kinetics of cake formation and desaturation. Although variations in coal properties probably have little effect on the filtration kinetics, they can significantly influence residual cake moisture. Moreover, the results obtained in this study indicate that there does not exist a single microstructure capable of providing both a high filtration rate and a low product moisture. Such a result is expected to influence future dewatering research efforts and possibly drive the design of new fine coal filtration technologies.