Toluene solutions of hydrophobic smectite (SAN) and polypropylene (PP) were mixed thoroughly. Trimethylsilylated SAN was also used to examine the effects of the surface modification. In both the smectites, the resulting mixtures were transparent but the stacked layer structures were retained, with expansion of the interlayer distance from 2.26 nm to similar to 5 nm. The PP containing the fine SAN filler particles was prepared after removal of toluene, followed by mixing with the PP to produce a 3 wt % SAN content. The SAN particles were more finely dispersed in the resulting composites than was achieved by conventional mechanical mixing, but the mechanical properties were not improved remarkably. The trimethylsilylation conferred no favourable effect on the mechanical properties of the composite.