The experimental sorption isotherms of fluoride were compared for several aluminosilicate clays. A competitive Langmuir isotherm incorporating pH dependence in fluoride sorption was used to model the experimental results. Bentonite was determined to be a far superior fluoride sorbent than kaolinite quantitatively, although results suggest that fluoride sorption by bentonite may not be achieved through the same sorption mechanism as for kaolinite. Factors found to influence fluoride sorption include solution pH, clay surface area, aluminium content and the presence of certain exchangeable cations capable of forming fluoride precipitates. Characterisation of fluoride sorption behaviour by clay mixtures was achieved through weighted averaging of the sorption behaviour for the individual clays of the mixture.